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D-Link NetDefend DFL-1660 User Manual

Manual is about: Network Security Firewall Application Control Signatures NetDefendOS

Summary of NetDefend DFL-1660

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    Network security solution http://www.Dlink.Com security security dfl-210/ 800/1600/ 2500 dfl-260/ 860/1660/ 2560(g) ver. 1.10 network security firewall user manual.

  • Page 2: User Manual

    User manual dfl-210/260/800/860/1600/1660/2500/2560/2560g netdefendos version 2.26 d-link corporation no. 289, sinhu 3rd rd, neihu district, taipei city 114, taiwan r.O.C. Http://www.Dlink.Com published 2009-09-08.

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    User manual dfl-210/260/800/860/1600/1660/2500/2560/2560g netdefendos version 2.26 published 2009-09-08 copyright notice this publication, including all photographs, illustrations and software, is protected under international copyright laws, with all rights reserved. Neither this manual, nor any of...

  • Page 4: Table Of Contents

    Table of contents preface ...............................................................................................................12 1. Netdefendos overview ....................................................................................14 1.1. Features ......................................

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    3.3. Interfaces ..............................................................................................84 3.3.1. Overview ...................................................................................84 3.3.2. Ethernet interfaces .............................................................

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    5.2. Dhcp servers ..................................................................................... 190 5.3. Static dhcp assignment ....................................................................... 193 5.3.1. Dhcp advanced settings .............................................................

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    7.3.6. Multiple sat rule matches ......................................................... 307 7.3.7. Sat and fwdfast rules .............................................................. 308 8. User authentication .........................................................................................

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    10.1.11. A summary of traffic shaping ................................................. 402 10.1.12. More pipe examples ............................................................... 402 10.2. Idp traffic shaping ............................................................................ 407 10.2....

  • Page 9: List Of Figures

    List of figures 1.1. Packet flow schematic part i ...........................................................................20 1.2. Packet flow schematic part ii ..........................................................................21 1.3. Packet flow schematic part iii ...........................

  • Page 10: List Of Examples

    List of examples 1. Example notation .............................................................................................12 2.1. Enabling remote management via https ...........................................................30 2.2. Enabling ssh remote access ..................................

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    4.13. If2 configuration - group translation ............................................................. 170 4.14. Setting up transparent mode for scenario 1 .................................................... 180 4.15. Setting up transparent mode for scenario 2 ......................................

  • Page 12: Preface

    Preface intended audience the target audience for this reference guide is administrators who are responsible for configuring and managing netdefend firewalls which are running the netdefendos operating system. This guide assumes that the reader has some basic knowledge of networks and network securi...

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    Items in the tree-view list at the left of the interface or in the menu bar or in a context menu need to be opened followed by information about the data items that need to be entered: 1. Go to item x > item y > item z 2. Now enter: • dataitem1: datavalue1 • dataitem2: datavalue2 highlighted content...

  • Page 14: 1.1. Features

    Chapter 1. Netdefendos overview this chapter outlines the key features of netdefendos. • features, page 14 • netdefendos architecture, page 17 • netdefendos state engine packet flow, page 20 1.1. Features d-link netdefendos is the base software engine that drives and controls the range of netdefend ...

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    Vpn netdefendos supports a range of virtual private network (vpn) solutions. Netdefendos supports ipsec, l2tp and pptp based vpns concurrently, can act as either server or client for all of the vpn types, and can provide individual security policies for each vpn tunnel. The details for this can be f...

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    Enables a device running netdefendos to distribute network load to multiple hosts. These features are discussed in detail in chapter 10, traffic management. Note threshold rules are only available on certain d-link netdefend product models. Operations and maintenance adminstrator management of netde...

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    1.2. Netdefendos architecture 1.2.1. State-based architecture the netdefendos architecture is centered around the concept of state-based connections. Traditional ip routers or switches commonly inspect all packets and then perform forwarding decisions based on information found in the packet headers...

  • Page 18: 1.2.3. Basic Packet Flow

    Netdefendos rule sets finally, rules which are defined by the administrator in the various rule sets are used for actually implementing netdefendos security policies. The most fundamental set of rules are the ip rules, which are used to define the layer 3 ip filtering policy as well as carrying out ...

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    • tcp/udp ports • icmp types • point in time in reference to a predefined schedule if a match cannot be found, the packet is dropped. If a rule is found that matches the new connection, the action parameter of the rule decides what netdefendos should do with the connection. If the action is drop, th...

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    1.3. Netdefendos state engine packet flow the diagrams in this section provide a summary of the flow of packets through the netdefendos state-engine. There are three diagrams, each flowing into the next. Figure 1.1. Packet flow schematic part i the packet flow is continued on the following page. 1.3...

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    Figure 1.2. Packet flow schematic part ii the packet flow is continued on the following page. 1.3. Netdefendos state engine packet flow chapter 1. Netdefendos overview 21.

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    Figure 1.3. Packet flow schematic part iii 1.3. Netdefendos state engine packet flow chapter 1. Netdefendos overview 22.

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    Apply rules the figure below presents the detailed logic of the apply rules function in figure 1.2, “packet flow schematic part ii” above. Figure 1.4. Expanded apply rules logic 1.3. Netdefendos state engine packet flow chapter 1. Netdefendos overview 23.

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    1.3. Netdefendos state engine packet flow chapter 1. Netdefendos overview 24.

  • Page 25: 2.1. Managing Netdefendos

    Chapter 2. Management and maintenance this chapter describes the management, operations and maintenance related aspects of netdefendos. • managing netdefendos, page 25 • events and logging, page 51 • radius accounting, page 56 • hardware monitoring, page 61 • snmp monitoring, page 63 • the pcapdump ...

  • Page 26: 2.1.3. The Web Interface

    This feature is fully described in section 2.1.6, “secure copy”. Console boot menu before netdefendos starts running, a console connected directly to the netdefend firewall's rs232 port can be used to do basic configuration through the boot menu. This menu can be entered by pressing any console key ...

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    Netdefendos provides an intuitive web interface (webui) for management of the system via an ethernet interface using a standard web browser. This allows the administrator to perform remote management from anywhere on a private network or the public internet using a standard computer without having t...

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    Password is admin and admin. If the user credentials are correct, you will be transferred to the main web interface page. First time web interface logon and the setup wizard when logging on for the first time, the default username is admin and the password is admin. After successful login, the webui...

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    For information about the default user name and password, see section 2.1.2, “the default administrator account”. Note: remote management access access to the web interface is regulated by the configured remote management policy. By default, the system will only allow web access from the internal ne...

  • Page 30: 2.1.4. The Cli

    Controlling access to the web interface by default, the web interface is accessible only from the internal network. If you need to enable access from other parts of the network, you can do so by modifying the remote management policy. Example 2.1. Enabling remote management via https cli gw-world:/>...

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    Is described below), or remotely via an ethernet interface using the secure shell (ssh) protocol from an ssh client. The cli provides a comprehensive set of commands that allow the display and modification of configuration data as well as allowing runtime data to be displayed and allowing system mai...

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    Command appears it can be re-executed in it's original form or changed first before execution. Tab completion remembering all the commands and their options can be difficult. Netdefendos provides a feature called tab completion which means that pressing the tab key will cause automatically completio...

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    Not all object types belong in a category. The object type userauthrule is a type without a category and will appear in the category list after pressing tab at the beginning of a command. The category is sometimes also referred to as a context. Selecting object categories with some categories, it is...

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    Can be done either by referring to it by its index, that is to say its list position, or by alternatively using the name assigned to it. The cli reference guide lists the parameter options available for each netdefendos object, including the name= and index= options. Using unique names for convenien...

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    4. Press the enter key on the terminal. The netdefendos login prompt should appear on the terminal screen. Ssh (secure shell) cli access the ssh (secure shell) protocol can be used to access the cli over the network from a remote host. Ssh is a protocol primarily used for secure communication over i...

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    Else as soon as possible after initial startup. User passwords can be any combination of characters and cannot be greater than 256 characters in length. It is recommended to use only printable characters. To change the password to, for example, my-password the following cli commands are used. First ...

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    Explicity checking configuration integrity after changing a configuration on the netdefend firewall, and before the activate/commit commands, it is possible to explicitly check for any problems in a configuration using the command: gw-world:/> show -errors this will cause netdefendos to scan the con...

  • Page 38: 2.1.5. Cli Scripts

    • web interface sessions connected by http or https. The command without any options gives a summary of currently open sessions: gw-world:/> sessionmanager session manager status ---------------------- active connections : 3 maximum allowed connections : 64 local idle session timeout : 900 netcon id...

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    Script variables a script file can contain any number of script variables which are called: $1, $2, $3, $4......$n the values substituted for these variable names are specified as a list at the end of the script -execute command line. The number n in the variable name indicates the variable value's ...

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    To move the example my_script.Sgs to non-volatile memory the command would be: gw-world:/> script -store -name=my_script.Sgs alternatively, all scripts can be moved to non-volatile memory with the command: gw-world:/> script -store -all listing scripts the script on its own, command without any para...

  • Page 41: 2.1.6. Secure Copy

    Then uploaded and executed on the other netdefend firewalls. The end result is that all units will have the same ip4address objects in their address book. The name of the file created using the -create option cannot be greater than 16 characters in length (including the extension) and the filetype s...

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    Download is done with the command: > scp the source or destination netdefend firewall is of the form: @:. For example: admin@10.62.11.10:config.Bak. The must be a defined netdefendos user in the administrator user group. Note: scp examples do not show the password prompt scp will normally prompt for...

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    Scripts”. • sshclientkey/ - the ssh client key object type. Examples of uploading and downloading in some cases, a file is located in the netdefendos root. The license file (license.Lic) falls into this category, as well as backup files for configurations (config.Bak) and the complete system (full.B...

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    If any console key is pressed during these 3 seconds then netdefendos startup pauses and the console boot menu is displayed. Initial boot menu options without a password set when netdefendos is started for the first time with no console password set for console access then the full set of boot menu ...

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    The 1. Start firewall option re-continues the interrupted netdefendos startup process. If the 2. Login option is chosen, the console password must be entered and the full boot menu described above is entered. Removing the console password once the console password is set it can be removed by selecti...

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    Default: 443 https certificate specifies which certificate to use for https traffic. Only rsa certificates are supported. Default: https 2.1.9. Working with configurations configuration objects the system configuration is built up by configuration objects, where each object represents a configurable...

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    Can be added to the list. • header - the header row displays the titles of the columns in the list. The tiny arrow images next to each title can be used for sorting the list according to that column. • rows - each row in the list corresponds to one configuration item. Most commonly, each row starts ...

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    Show the object again to verify the new property value: gw-world:/> show service servicetcpudp telnet property value ----------------- ------- name: telnet destinationports: 23 type: tcp sourceports: 0-65535 synrelay: no passicmpreturn: no alg: (none) maxsessions: 1000 comments: modified comment web...

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    6. Click ok 7. Verify that the new ip4 address object has been added to the list example 2.7. Deleting a configuration object this example shows how to delete the newly added ip4address object. Cli gw-world:/> delete address ip4address myhost web interface 1. Go to objects > address book 2. Right-cl...

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    * servicetcpudp telnet a "+" character in front of the row indicates that the object has been added. A "*" character indicates that the object has been modified. A "-" character indicates that the object has been marked for deletion. Web interface 1. Go to configuration > view changes in the menu ba...

  • Page 51: 2.2. Events And Logging

    2.2. Events and logging 2.2.1. Overview the ability to log and analyze system activities is an essential feature of netdefendos. Logging enables not only monitoring of system status and health, but also allows auditing of network usage and assists in trouble-shooting. Log message generation netdefen...

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    By default all messages of level info and above are sent. The debug category of designed for troubleshooting only and should only be turned on if required to try and solve a problem. Messages of all severity levels are found listed in the netdefendos log reference guide. 2.2.3. Log message distribut...

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    In order to facilitate automated processing of all messages, netdefendos writes all log data to a single line of text. All data following the initial text is presented in the format name=value. This enables automatic filters to easily find the values they are looking for without assuming that a spec...

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    By d-link and defines the snmp objects and data types that are used to describe an snmp trap received from netdefendos. Note there is a different mib file for each model of netdefend firewall. Make sure that the correct file is used. For each netdefend firewall model there is one generic trap object...

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    Send limit this setting limits how many log packets netdefendos may send out per second. This value should never be set too low, as this may result in important events not being logged, nor should it be set too high. A situation where setting too high a value may cause damage is when netdefendos sen...

  • Page 56: 2.3. Radius Accounting

    2.3. Radius accounting 2.3.1. Overview within a network environment containing large numbers of users, it is advantageous to have one or a cluster of central servers that maintain user account information and are responsible for authentication and authorization tasks. The central database residing o...

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    Authentication server. • how authenticated - how the user was authenticated. This is set to either radius if the user was authenticated via radius, or local if the user was authenticated via a local user database. • delay time - the time delay (in seconds) since the accountingrequest packet was sent...

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    Tip: the meaning of an asterisk in the list the asterisk "*" symbol in the above list indicates that the sending of the parameter is user configurable. 2.3.3. Interim accounting messages in addition to start and stop messages netdefendos can optionally periodically send interim accounting messages t...

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    Firewalls. This means that accounting information is automatically updated on both cluster members whenever a connection is closed. Two special accounting events are also used by the active unit to keep the passive unit synchronized: • an accountingstart event is sent to the inactive member in an ha...

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    Continue to be logged in. Disabling the setting will mean that the user will be logged out if the radius accounting server cannot be reached even though the user has been previously authenticated. Default: enabled logout at shutdown if there is an orderly shutdown of the netdefend firewall by the ad...

  • Page 61: 2.4. Hardware Monitoring

    2.4. Hardware monitoring availability certain d-link hardware models allow the administrator to use the cli to query the current value of various hardware operational parameters such as the current temperature inside the firewall. This feature is referred to as hardware monitoring. The d-link netdef...

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    The -verbose option displays the current values plus the configured ranges: gw-world:/> hwm -a -v 2 sensors available poll interval time = 500ms name [type][number] = low_limit] current_value [high_limit (unit) ----------------------------------------------------------------- sys temp [temp ][ 0] = ...

  • Page 63: 2.5. Snmp Monitoring

    2.5. Snmp monitoring overview simple network management protocol (snmp) is a standardized protocol for management of network devices. An snmp compliant client can connect to a network device which supports the snmp protocol to query and control it. Netdefendos supports snmp version 1 and version 2. ...

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    Snmp access. Port 161 is usually used for snmp and netdefendos always expects snmp traffic on that port. Remote access encryption it should be noted that snmp version 1 or 2c access means that the community string will be sent as plain text over a network. This is clearly insecure if a remote client...

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    Default: enabled snmp request limit maximum number of snmp requests that will be processed each second by netdefendos. Should snmp requests exceed this rate then the excess requests will be ignored by netdefendos. Default: 100 system contact the contact person for the managed node. Default: n/a syst...

  • Page 66: 2.6. The Pcapdump Command

    2.6. The pcapdump command a valuable diagnostic tool is the ability to examine the packets that enter and leave the interfaces of a netdefend firewall. For this purpose, netdefendos provides the cli command pcapdump which not only allows the examination of packet streams entering and leaving interfa...

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    It is possible to have multiple pcapdump executions being performed at the same time. The following points describe this feature: 1. All capture from all executions goes to the same memory buffer. The command can be launched multiple times with different interfaces specified. In this case the packet...

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    • the filename and extension can only contain the characters a-z, 0-9, "-" and "_". Combining filters it is possible to use several of these filter expressions together in order to further refine the packets that are of interest. For example we might want to examine the packets going to a particular...

  • Page 69: 2.7. Maintenance

    2.7. Maintenance 2.7.1. Auto-update mechanism a number of the netdefendos security features rely on external servers for automatic updates and content filtering. The intrusion prevention and detection system and anti-virus modules require access to updated signature databases in order to provide pro...

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    Be altered to include the date. For example, full.Bak might become full-20081121.Bak to show it is a snapshot of the state on november 21st, 2008. To restore a backup file, the administrator should upload the file to the netdefend firewall. The name of the file does not need to be changed in any way...

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    Important: any upgrades will be lost after a factory reset it should be understood that a reset to factory defaults is exactly that. Any netdefendos upgrades performed since the unit left the factory will be lost. Reset procedure for the netdefend dfl-210, 260, 800 and 860 to reset the netdefend dfl...

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    2.7.3. Restore to factory defaults chapter 2. Management and maintenance 72.

  • Page 73: Chapter 3. Fundamentals

    Chapter 3. Fundamentals this chapter describes the fundamental logical objects which make up a netdefendos configuration. These objects include such items as ip addresses and ip rules. Some exist by default and some must be defined by the administrator. In addition, the chapter explains the differen...

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    Corresponds to a 32 address net (netmask 255.255.255.224) and so on. The numbers 0-32 correspond to the number of binary ones in the netmask. For example: 192.168.0.0/24. Ip range a range of ip addresses is represented on the form a.B.C.D - e.F.G.H. Note that ranges are not limited to netmask bounda...

  • Page 75: 3.1.3. Ethernet Addresses

    Web interface 1. Go to objects > address book > add > ip address 2. Specify a suitable name for the ip range, for example wwwservers. 3. Enter 192.168.10.16-192.168.10.21 as the ip address 4. Click ok example 3.4. Deleting an address object to delete an object named wwwsrv1 in the address book, do t...

  • Page 76: 3.1.4. Address Groups

    Web interface 1. Go to objects > address book > add > ethernet address 2. Specify a suitable name for the ethernet address object, for example wwwsrv1_mac 3. Enter 08-a3-67-bc-2e-f2 as the mac address 4. Click ok 3.1.4. Address groups groups simplify configuration address objects can be grouped in o...

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    Otherwise, the object will be left empty (in other words, the ip address will be 0.0.0.0/0). All-nets the all-nets ip address object is initialized to the ip address 0.0.0.0/0, which represents all possible ip addresses. The all-nets ip object is used extensively in the configuration of netdefendos ...

  • Page 78: 3.2. Services

    3.2. Services 3.2.1. Overview a service object is a reference to a specific ip protocol with associated parameters. A service definition is usually based on one of the major transport protocols such as tcp or udp, with the associated port number(s). The http service, for instance, is defined as usin...

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    To view a specific service in the system: cli gw-world:/> show service servicetcpudp echo the output will look similar to the following listing: property value ----------------- ---------------- name: echo destinationports: 7 type: tcpudp (tcp/udp) sourceports: 0-65535 passicmpreturn: no alg: (none)...

  • Page 80

    Port ranges some services use a range of destination ports. As an example, the netbios protocol used by microsoft windows uses destination ports 137 to 139. To define a range of ports in a tcp/udp service object, the format mmm-nnn is used. A port range is inclusive, meaning that a range specified a...

  • Page 81: 3.2.3. Icmp Services

    Gateway (alg) to enable deeper inspection of certain protocols. For more information see section 6.2, “algs”. Max sessions an important parameter associated with a service is max sessions. This parameter is allocated a default value when the service is associated with an alg. The default value varie...

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    • code 4: cannot fragment • code 5: source route failed • redirect: the source is told that there is a better route for a particular packet. Codes assigned are as follows: • code 0: redirect datagrams for the network • code 1: redirect datagrams for the host • code 2: redirect datagrams for the type...

  • Page 83: 3.2.5. Service Groups

    4. Optionally enter virtual router redundancy protocol in the comments control 5. Click ok 3.2.5. Service groups a service group is, exactly as the name suggests, a netdefendos object that consists of a collection of services. Although the group concept is simple, it can be very useful when construc...

  • Page 84: 3.3. Interfaces

    3.3. Interfaces 3.3.1. Overview an interface is one of the most important logical building blocks in netdefendos. All network traffic that passes through or gets terminated in the system is done so through one or several interfaces. An interface can be seen as a doorway for network traffic to or fro...

  • Page 85: 3.3.2. Ethernet Interfaces

    Found in section 9.5, “pptp/l2tp”. • gre interfaces are used to establish gre tunnels. More information about this topic can be found in section 3.3.5, “gre tunnels”. Even though the various types of interfaces are very different in the way they are implemented and how they work, netdefendos treats ...

  • Page 86

    Progressively smaller as the transmission rates get faster from normal ethernet to fast ethernet and then gigabit ethernet. Each netdefendos ethernet interface corresponds to a physical ethernet port in the system. The number of ports, their link speed and the way the ports are realized, is dependen...

  • Page 87

    • instead, the ip_lan object in the netdefendos address book should be assigned the new address since it is this object that is used by many other netdefendos objects such as ip rules. The cli command to do this would be: gw-world:/> set address ip4address ip_lan address=10.1.1.2 this same operation...

  • Page 88

    Web interface 1. Go to interfaces > ethernet 2. Select the ethernet interface of interest 3. Enable the enable dhcp client option 4. Click ok 3.3.2.1. Useful cli commands for ethernet interfaces this section summarizes the cli commands most commonly used for examining and manipulating netdefendos et...

  • Page 89

    Here, tab completion is used again at the end of the command line: gw-world:/> set address ip4address [] []: dnsserver1_ip interfaceaddresses/wan_br timesyncsrv1_ip interfaceaddresses/aux_ip interfaceaddresses/wan_dns1 interfaceaddresses/aux_net interfaceaddresses/wan_dns2 interfaceaddresses/dmz_ip ...

  • Page 90: 3.3.3. Vlan

    For a complete list of all cli options see the cli reference guide. 3.3.3. Vlan overview virtual lan (vlan) support in netdefendos allows the definition of one or more virtual lan interfaces which are associated with a particular physical interface. These are then considered to be logical interfaces...

  • Page 91

    With netdefendos vlans, the physical connections are as follows: • one of more vlans are configured on a physical netdefend firewall interface and this is connected directly to a switch. This link acts as a vlan trunk. The switch used must support port based vlans. This means that each port on the s...

  • Page 92

    The number of vlan interfaces that can be defined for a netdefendos installation is limited by the parameters of the license used. Different hardware models have different licenses and different limits on vlans. Summary of vlan setup it is important to understand that the administrator should treat ...

  • Page 93: 3.3.4. Pppoe

    3.3.4. Pppoe 3.3.4.1. Overview point-to-point protocol over ethernet (pppoe) is a tunneling protocol used for connecting multiple users on an ethernet network to the internet through a common serial interface, such as a single dsl line, wireless device or cable modem. All the users on the ethernet s...

  • Page 94

    Receives this ip address information from the isp, it stores it in a network object and uses it as the ip address of the interface. User authentication if user authentication is required by the isp, the username and password can be setup in netdefendos for automatic sending to the pppoe server. Dial...

  • Page 95: 3.3.5. Gre Tunnels

    • service name: service name provided by the service provider • username: username provided by the service provider • password: password provided by the service provider • confirm password: retype the password • under authentication specify which authentication protocol to use (the default settings ...

  • Page 96

    Like other tunnels in netdefendos such as an ipsec tunnel, a gre tunnel is treated as a logical interface by netdefendos, with the same filtering, traffic shaping and configuration capabilities as a standard interface. The gre options are: • ip address - this is the ip address of the sending interfa...

  • Page 97

    The diagram above shows a typical gre scenario, where two netdefend firewalls a and b must communicate with each other through the intervening internal network 172.16.0.0/16. Any traffic passing between a and b is tunneled through the intervening network using a gre tunnel and since the network is i...

  • Page 98: 3.3.6. Interface Groups

    • remote endpoint: remote_gw • use session key: 1 • additional encapulation checksum: enabled 3. Define a route in the main routing table which routes all traffic to remote_net_a on the gre_to_a gre interface. This is not necessary if the option add route for remote network is enabled in the advance...

  • Page 99: 3.4. Arp

    3.4. Arp 3.4.1. Overview address resolution protocol (arp) is a protocol, which maps a network layer protocol address to a data link layer hardware address and it is used to resolve an ip address into its corresponding ethernet address. Arp operates at the osi data link layer (layer 2 - see appendix...

  • Page 100

    The default expiration time for dynamic arp entries is 900 seconds (15 minutes). This can be changed by modifying the advanced setting arp expire. The setting arp expire unknown specifies how long netdefendos will remember addresses that cannot be reached. This is done to ensure that netdefendos doe...

  • Page 101

    Hash size for vlan interfaces only. The default value is 64. 3.4.4. Static and published arp entries netdefendos supports defining static arp entries (static binding of ip addresses to ethernet addresses) as well as publishing ip addresses with a specific ethernet address. Static arp entries static ...

  • Page 102

    The corresponding netdefendos interface. Another use is publishing multiple addresses on an external interface, enabling netdefendos to statically address translate communications to these addresses and send it onwards to internal servers with private ip addresses. There are two publishing modes; pu...

  • Page 103

    Allowing this to take place may allow hijacking of local connections. However, not allowing this may cause problems if, for example, a network adapter is replaced, as netdefendos will not accept the new address until the previous arp cache entry has timed out. The advanced setting arp changes can be...

  • Page 104

    Default: droplog arp requests determines if netdefendos will automatically add the data in arp requests to its arp table. The arp specification states that this should be done, but as this procedure can facilitate hijacking of local connections, it is not normally allowed. Even if arprequests is set...

  • Page 105

    Broadcast addresses. Such claims are usually never correct. Default: droplog arp cache size how many arp entries there can be in the cache in total. Default: 4096 arp hash size hashing is used to rapidly look up entries in a table. For maximum efficiency, the hash size should be twice as large as th...

  • Page 106: 3.5. The Ip Rule Set

    3.5. The ip rule set 3.5.1. Security policies common policy characteristics netdefendos security policies designed by the administrator, regulate the way in which traffic can flow through the netdefend firewall. Policies in netdefendos are defined by different netdefendos rule sets. These rule sets ...

  • Page 107

    And are described in chapter 8, user authentication. Specifying any interface or network when specifying the filtering criteria in any of the rule sets specified above there are three useful predefined options that can be used: • for a source or destination network, the all-nets option is equivalent...

  • Page 108: 3.5.2. Ip Rule Evaluation

    If the ip rule used is an allow rule then this is bi-directional by default. The ordering of these steps is important. The route lookup occurs first to determine the exiting interface and then netdefendos looks for an ip rule that allows the traffic to leave on that interface. If a rule doesn't exis...

  • Page 109: 3.5.3. Ip Rule Actions

    Stateful inspection after initial rule evaluation of the opening connection, subsequent packets belonging to that connection will not need to be evaluated individually against the rule set. Instead, a highly efficient algorithm searches the state table for each packet to determine if it belongs to a...

  • Page 110

    Sat this tells netdefendos to perform static address translation. A sat rule always requires a matching allow, nat or fwdfast ip rule further down the rule set (see section 7.3, “sat” in chapter 7, address translation for a detailed description). Drop this tells netdefendos to immediately discard th...

  • Page 111

    Name and can then be used to contain all the ip rules that are related together as a group. Using folders is simply a way for the administrator to conveniently divide up ip rule set entries and no special properties are given to entries in different folders. Netdefendos continues to see all entries ...

  • Page 112: 3.6. Schedules

    3.6. Schedules in some scenarios, it might be useful to control not only what functionality is enabled, but also when that functionality is being used. For instance, the it policy of an enterprise might stipulate that web traffic from a certain department is only allowed access outside that departme...

  • Page 113

    Return to the top level: gw-world:/main> cc configuration changes must be saved by then issuing an activate followed by a commit command. Web interface 1. Go to objects > schedules > add > schedule 2. Enter the following: • name: officehours 3. Select 08-17, monday to friday in the grid 4. Click ok ...

  • Page 114: 3.7. Certificates

    3.7. Certificates 3.7.1. Overview x.509 netdefendos supports digital certificates that comply with the itu-t x.509 standard. This involves the use of an x.509 certificate hierarchy with public-key cryptography to accomplish key distribution and entity authentication. References in this manual to a c...

  • Page 115

    Validity time a certificate is not valid forever. Each certificate contains the dates between which the certificate is valid. When this validity period expires, the certificate can no longer be used, and a new certificate has to be issued. Important make sure the netdefendos date and time are set co...

  • Page 116

    There are two types of certificates that can be uploaded: self-signed certificates and remote certificates belonging to a remote peer or ca server. Self-signed certificates can be generated by using one of a number of freely available utilities for doing this. Example 3.19. Uploading a certificate t...

  • Page 117

    • take out the relevant parts of the .Pem file to form the required .Cer and .Key files. The detailed steps for the above stages are as follows: 1. Create the gateway certificate on the windows ca server and export it to a .Pfx file on the local netdefendos management workstation disk. 2. Now conver...

  • Page 118: 3.8. Date And Time

    3.8. Date and time 3.8.1. Overview correctly setting the date and time is important for netdefendos to operate properly. Time scheduled policies, auto-update of the idp and anti-virus databases, and other product features require that the system clock is accurately set. In addition, log messages are...

  • Page 119: 3.8.3. Time Servers

    Counted as being inside a given time zone will then have the same local time and this will be one of the integer offsets from gmt. The netdefendos time zone setting reflects the time zone where the netdefend firewall is physically located. Example 3.22. Setting the time zone to modify the netdefendo...

  • Page 120

    Netdefendos is able to adjust the clock automatically based on information received from one or more time servers which provide a highly accurate time, usually using atomic clocks. Using time servers is highly recommended as it ensures netdefendos will have its date and time aligned with other netwo...

  • Page 121

    The time server urls must have the prefix dns: to specify that they should be resolved with a dns server. Netdefendos must therefore also have a dns server defined so this resolution can be performed. Note if the timesyncinterval parameter is not specified when using the cli to set the synchronizati...

  • Page 122

    Example 3.27. Forcing time synchronization this example demonstrates how to force time synchronization, overiding the maximum adjustment setting. Cli gw-world:/> time -sync -force synchronization intervals the interval between each synchronization attempt can be adjusted if needed. By default, this ...

  • Page 123

    Dst offset daylight saving time offset in minutes. Default: 0 dst start date what month and day dst starts, in the format mm-dd. Default: none dst end date what month and day dst ends, in the format mm-dd. Default: none time sync server type type of server for time synchronization, udptime or sntp (...

  • Page 124

    Group interval interval according to which server responses will be grouped. Default: 10 3.8.4. Settings summary for date and time chapter 3. Fundamentals 124.

  • Page 125: 3.9. Dns

    3.9. Dns overview a dns server can resolve a fully qualified domain name (fqdn) into the corresponding numeric ip address. Fqdns are unambiguous textual domain names which specify a node's unique position in the internet's dns tree hierarchy. Fqdn resolution allows the actual physical ip address to ...

  • Page 126

    Dynamic dns a dns feature offered by netdefendos is the ability to explicitly inform dns servers when the external ip address of the netdefend firewall has changed. This is sometimes referred to as dynamic dns and is useful where the netdefend firewall has an external ip address that can change. Dyn...

  • Page 127

    3.9. Dns chapter 3. Fundamentals 127.

  • Page 128: Chapter 4. Routing

    Chapter 4. Routing this chapter describes how to configure ip routing in netdefendos. • overview, page 128 • static routing, page 129 • policy-based routing, page 143 • route load balancing, page 148 • dynamic routing, page 154 • multicast routing, page 162 • transparent mode, page 174 4.1. Overview...

  • Page 129: 4.2. Static Routing

    4.2. Static routing the most basic form of routing is known as static routing. The word "static" refers to the fact that entries in the routing table are manually added and are therefore permanent (or static) by nature. Due to this manual approach, static routing is most appropriate to use in smalle...

  • Page 130

    This parameter usually doesn't need to be specified. If it is specified, netdefendos responds to arp queries sent to this address. A special section below explains this parameter in more depth. Local ip address and gateway are mutually exclusive and either one or the other should be specified. • met...

  • Page 131

    The above routing table provides the following information: • route #1 all packets going to hosts on the 192.168.0.0/24 network should be sent out on the lan interface. As no gateway is specified for the route entry, the host is assumed to be located on the network segment directly reachable from th...

  • Page 132

    • local ip address: an address within the second network's ip range. When the default gateway of the second network's clients is now set to the same value as the local ip address of the above route, the clients will be able to communicate successfully with the interface. The ip address chosen in the...

  • Page 133: 4.2.2. Static Routing

    Network of a connection but also for the source network. The route that defines the source network simply says that the source network is found on a particular interface. When a new connection is opened, netdefendos performs a check known as a reverse route lookup which looks for this route. The sou...

  • Page 134

    0.0.0.0 0.0.0.0 192.168.0.1 192.168.0.10 20 10.0.0.0 255.0.0.0 10.4.2.143 10.4.2.143 1 10.4.2.143 255.255.255.255 127.0.0.1 127.0.0.1 50 10.255.255.255 255.255.255.255 10.4.2.143 10.4.2.143 50 85.11.194.33 255.255.255.255 192.168.0.1 192.168.0.10 20 127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1 192.168....

  • Page 135

    Gw-world:/main> show route # interface network gateway local ip - --------- -------- ------------- -------- 1 wan all-nets 213.124.165.1 (none) 2 lan lannet (none) (none) 3 wan wannet (none) (none) to see the active routing table enter: gw-world:/> routes flags network iface gateway local ip metric ...

  • Page 136

    However, the option also exists for any physical interface to indicate that it should be used for connection to the internet. In the web interface this is an advanced setting in the ethernet interface properties called: automatically add a default route for this interface using the given default gat...

  • Page 137: 4.2.3. Route Failover

    Tip: understanding output from the routes command for detailed information about the output of the cli routes command. Please see the cli reference guide. 4.2.3. Route failover overview netdefend firewalls are often deployed in mission-critical locations where availability and connectivity is crucia...

  • Page 138

    Instantly noticed, this method provides the fastest response to failure. Gateway monitoring if a specific gateway has been specified as the next hop for a route, accessibility to that gateway can be monitored by sending periodic arp requests. As long as the gateway responds to these requests, the ro...

  • Page 139

    Route interface grouping when using route monitoring, it is important to check if a failover to another route will cause the routing interface to be changed. If this could happen, it is necessary to take some precautionary steps to ensure that policies and existing connections will be maintained. To...

  • Page 140

    The advantages of host monitoring are twofold: • in a complex network topology it is more reliable to check accessibility to external hosts. Just monitoring a link to a local switch may not indicate a problem in another part of the internal network. • host monitoring can be used to help in setting t...

  • Page 141: 4.2.5. Proxy Arp

    • sample the number of polling attempts used as a sample size for calculating the percentage loss and the average latency. This value cannot be less than 1. • maximum failed poll attempts the maximum permissible number of polling attempts that fail. If this number is exceeded then the host is consid...

  • Page 142

    Overview as discussed previously in section 3.4, “arp”, the arp protocol facilitates a mapping between an ip address and the mac address of a node on an ethernet network. However, situations may exist where a network running ethernet is separated into two parts with a routing device such as an insta...

  • Page 143: 4.3. Policy-Based Routing

    4.3. Policy-based routing 4.3.1. Overview policy-based routing (pbr) is an extension to the standard routing described previously. It offers administrators significant flexibility in implementing routing decision policies by being able to define rules so alternative routing tables are used. Normal r...

  • Page 144

    When looking up policy-based rules, it is the first matching rule found that is triggered. 4.3.4. Pbr table selection when a packet corresponding to a new connection first arrives, the processing steps are as follows to determine which routing table is chosen: 1. The pbr rules must first be looked u...

  • Page 145

    Important: ensure all-nets appears in the main table a common mistake with policy-based routing is the absence of the default route with a destination interface of all-nets in the default main routing table. If there is no route that is an exact match then the absence of a default all-nets route wil...

  • Page 146

    This example illustrates a multiple isp scenario which is a common use of policy-based routing. The following is assumed: • each isp will give you an ip network from its network range. We will assume a 2-isp scenario, with the network 10.10.10.0/24 belonging to isp a and 20.20.20.0/24 belonging to i...

  • Page 147

    Note rules in the above example are added for both inbound and outbound connections. 4.3.5. The ordering parameter chapter 4. Routing 147.

  • Page 148: 4.4. Route Load Balancing

    4.4. Route load balancing overview netdefendos provides the option to perform route load balancing (rlb). This is the ability to distribute traffic over multiple alternate routes based on a number of predefined distribution algorithms. The purpose of this feature is to provide the following: • balan...

  • Page 149

    3. If more than one matching route is found then rlb is used to choose which one to use. This is done according to which algorithm is selected in the table's rlb instance object: • round robin successive routes are chosen from the matching routes in a "round robin" fashion provided that the metric o...

  • Page 150

    Spillover limits are set separately for ingoing and outgoing traffic with only one of these typically being specified. If both are specified then only one of them needs to be exceeded continuously for hold timer seconds for the next matching route to be chosen. The units of the limits, such as mbps,...

  • Page 151

    Several alternative routes can be set up, each with their own interface limits and each with a different metric. The route with the lowest metric is chosen first and when that route's interface limits are exceeded, the route with the next highest metric is then chosen. When that new route's interfac...

  • Page 152

    To the firewall interfaces wan1 and wan2. Rlb will be used to balance the connections between the two isps. Figure 4.5. A route load balancing scenario we first need to define two routes to these two isps in the main routing table as shown below: route no. Interface destination gateway metric 1 wan1...

  • Page 153

    Achieve stickiness so the server always sees the same source ip address (wan1 or wan2) from a single client. Cli gw-world:/> add routebalancinginstance main algorithm=destination web interface 1. Go to routing > route load balancing > instances > add > route balancing instance 2. The route balancing...

  • Page 154: 4.5. Dynamic Routing

    4.5. Dynamic routing 4.5.1. Dynamic routing overview dynamic routing is different to static routing in that the netdefend firewall will adapt to changes of network topology or traffic load automatically. Netdefendos first learns of all the directly connected networks and gets further route informati...

  • Page 155: 4.5.2. Ospf

    Ospf is not available on the dfl-210 and 260. Comparing dynamic routing algorithms due to the fact that the global link state information is maintained everywhere in a network, ls algorithms offer a high degree of configuration control and scalability. Changes result in broadcasts of just the update...

  • Page 156

    Link-state routing ospf is a form of link-state routing protocol that defines the sending of link-state advertisements (lsas) to all other routers within the same area. Each router maintains a database, known as a link-state database, describing the as topology. From the information in this database...

  • Page 157

    Neighbors routers that are in the same area become neighbors in that area. Neighbors are elected via the hello protocol. Hello packets are sent periodically out of each interface using ip multicast. Routers become neighbors as soon as they see themselves listed in the neighbor's hello packet. This w...

  • Page 158

    In the above example, the virtual link is configured between fw1 and fw2 on area 1, as it is used as the transit area. In this configuration only the router id has to be configured. The diagram shows that fw2 needs to have a virtual link to fw1 with router id 192.168.1.1 and vice versa. These virtua...

  • Page 159

    The virtual link is configured between fw1 and fw2 on area 1, as it is used as the transit area. In the configuration only the router id have to be configured, as in the example above show fw2 need to have a virtual link to fw1 with the router id 192.168.1.1 and vice versa. These vlinks need to be c...

  • Page 160

    Example 4.7. Importing routes from an ospf as into the main routing table in this example, the routes received using ospf will be added into the main routing table. First of all a dynamic routing policy filter needs to be created. The filter needs to have a name, in this example importospfroutes is ...

  • Page 161

    Web interface 1. Go to routing > dynamic routing rules > add > dynamic routing policy rule 2. Specify a suitable name for the filter, for example exportdefroute 3. For from routing table select main routing table 4. Choose wan for destination interface 5. Choose all-nets in the ...Exactly matches li...

  • Page 162: 4.6. Multicast Routing

    4.6. Multicast routing 4.6.1. Overview certain types of internet interactions, such as conferencing and video broadcasts, require a single client or host to send the same packet to multiple receivers. This could be achieved through the sender duplicating the packet with different receiving ip addres...

  • Page 163

    The multiplex rule can operate in one of two modes: using igmp the traffic flow specified by the multiplex rule must have been requested by hosts using igmp before any multicast packets are forwarded through the specified interfaces. This is the default behavior of netdefendos. Not using igmp the tr...

  • Page 164

    The matching rule could also be a nat rule for source address translation (see below) but cannot be a fwdfast or sat rule. Example 4.9. Forwarding of multicast traffic using the sat multiplex rule in this example, we will create a multiplex rule in order to forward the multicast groups 239.192.10.0/...

  • Page 165

    The cli command to create the multiplex rule is then: add iprule sourcenetwork= sourceinterface= destinationinterface= destinationnetwork= action=multiplexsat service= multiplexargument={outif1;ip1},{outif2;ip2},{outif3;ip3}... The two values {outif;ip} represent a combination of output interface an...

  • Page 166: 4.6.3. Igmp Configuration

    Example 4.10. Multicast forwarding - address translation the following sat multiplex rule needs to be configured to match the scenario described above: web interface a. Create a custom service for multicast called multicast_service: 1. Go to objects > services > add > tcp/udp 2. Now enter: • name: m...

  • Page 167

    The multicast source is located on a network directly connected to the router. In this case, no query rule is needed. A second exception is if a neighboring router is statically configured to deliver a multicast stream to the netdefend firewall. In this case also, an igmp query would not have to be ...

  • Page 168

    4.6.3.1. Igmp rules configuration - no address translation this example describes the igmp rules needed for configuring igmp according to the no address translation scenario described above. We want our router to act as a host towards the upstream router and therefore we configure igmp to run in pro...

  • Page 169

    • multicast source: 192.168.10.1 • multicast group: 239.192.10.0/24 4. Click ok 4.6.3.2. Igmp rules configuration - address translation the following examples illustrates the igmp rules needed to configure igmp according to the address translation scenario described above in section 4.6.2.2, “multic...

  • Page 170

    • output: if1 (this is the relay interface) 3. Under address filter enter: • source interface: wan • source network: upstreamrouterip • destination interface: core • destination network: auto • multicast source: 192.168.10.1 • multicast group: 239.192.10.0/24 4. Click ok example 4.13. If2 configurat...

  • Page 171

    3. Under address filter enter: • source interface: wan • source network: upstreamrouterip • destination interface: core • destination network: auto • multicast source: 192.168.10.1 • multicast group: 239.192.10.0/24 4. Click ok advanced igmp settings there are a number of igmp advanced settings whic...

  • Page 172

    Default: igmpv3 igmp last member query interval the maximum time in milliseconds until a host has to send an answer to a group or group-and-source specific query. Global setting on interfaces without an overriding igmp setting. Default: 5,000 igmp max total requests the maximum global number of igmp...

  • Page 173

    Interfaces without an overriding igmp setting. Default: 30,000 igmp unsolicated report interval the time in milliseconds between repetitions of an initial membership report. Global setting on interfaces without an overriding igmp setting. Default: 1,000 4.6.4. Advanced igmp settings chapter 4. Routi...

  • Page 174: 4.7. Transparent Mode

    4.7. Transparent mode 4.7.1. Overview transparent mode usage the netdefendos transparent mode feature allows a netdefend firewall to be placed at a point in a network without any reconfiguration of the network and without hosts being aware of its presence. All netdefendos features can then be used t...

  • Page 175

    . If the netdefend firewall is placed into a network for the first time, or if network topology changes, the routing configuration must therefore be checked and adjusted to ensure that the routing table is consistent with the new layout. Reconfiguration of ip settings may be required for pre-existin...

  • Page 176

    Discovery is done by netdefendos sending out arp as well as icmp (ping) requests, acting as the initiating sender of the original ip packet for the destination on the interfaces specified in the switch route. If an arp reply is received, netdefendos will update the cam table and layer 3 cache and fo...

  • Page 177

    Associated with the switch routes, transparency will exist between them. For example, if the interfaces if1 to if6 appear in a switch routes in routing table a, the resulting interconnections will be as illustrated below. Connecting together switch routes in this way only applies, however, if all in...

  • Page 178

    The recommended way to enable transparent mode is to add switch routes, as described above. An alternative method is to enable transparent mode directly on an interface (a check box for this is provided in the graphical user interfaces). When enabled in this way, default switch routes are automatica...

  • Page 179

    Transparent mode with a common address range (in this example 192.168.10.0/24). Figure 4.13. Transparent mode internet access in this situation, any "normal" non-switch all-nets routes in the routing table should be removed and replaced with an all-nets switch route (not doing this is a common mista...

  • Page 180

    The other consequence of not using nat is that ip addresses of users accessing the internet usually need to be public ip addresses. If nating needs to be performed in the example above to hide individual addresses from the internet, it would have to be done by a device (possibly another netdefend fi...

  • Page 181

    5. Now enter: • ip address: 10.0.0.2 • network: 10.0.0.0/24 • transparent mode: enable 6. Click ok configure the rules: 1. Go to rules > ip rules > add > iprule 2. Now enter: • name: httpallow • action: allow • service: http • source interface: lan • destination interface: any • source network: 10.0...

  • Page 182

    Example 4.15. Setting up transparent mode for scenario 2 configure a switch route over the lan and dmz interfaces for address range 10.0.0.0/24 (assume the wan interface is already configured). Web interface configure the interfaces: 1. Go to interfaces > ethernet > edit (lan) 2. Now enter: • ip add...

  • Page 183

    • interfaces: select lan and dmz 3. Click ok configure the routing: 1. Go to routing > main routing table > add > switchroute 2. Now enter: • switched interfaces: transparentgroup • network: 10.0.0.0/24 • metric: 0 3. Click ok configure the rules: 1. Go to rules > ip rules > add > iprule 2. Now ente...

  • Page 184

    • destination interface: dmz • source network: all-nets • destination network: wan_ip 9. Click ok 4.7.4. Spanning tree bpdu support netdefendos includes support for relaying the bridge protocol data units (bpdus) across the netdefend firewall. Bpdu frames carry spanning tree protocol (stp) messages ...

  • Page 185

    Default: enabled decrement ttl enable this if the ttl should be decremented each time a packet traverses the firewall in transparent mode. Default: disabled dynamic cam size this setting can be used to manually configure the size of the cam table. Normally dynamic is the preferred value to use. Defa...

  • Page 186

    Null enet sender defines what to do when receiving a packet that has the sender hardware (mac) address in ethernet header set to null (0000:0000:0000). Options: • drop - drop packets • droplog - drop and log packets default: droplog broadcast enet sender defines what to do when receiving a packet th...

  • Page 187

    • drop - drop the packets • droplog - drop packets log the event default: drop relay mpls when set to ignore all incoming mpls packets are relayed in transparent mode. Options: • ignore - let the packets pass but do not log • log - let the packets pass and log the event • drop - drop the packets • d...

  • Page 188

    4.7.5. Advanced settings for transparent mode chapter 4. Routing 188.

  • Page 189: Chapter 5. Dhcp Services

    Chapter 5. Dhcp services this chapter describes dhcp services in netdefendos. • overview, page 189 • dhcp servers, page 190 • static dhcp assignment, page 193 • dhcp relaying, page 195 • ip pools, page 198 5.1. Overview dynamic host configuration protocol (dhcp) is a protocol that allows network adm...

  • Page 190: 5.2. Dhcp Servers

    5.2. Dhcp servers dhcp servers assign and manage the ip addresses taken from a specified address pool. In netdefendos, dhcp servers are not limited to serving a single range of ip addresses but can use any ip address range that can be specified by a netdefendos ip address object. Multiple dhcp serve...

  • Page 191

    • wins servers - wins servers the client can use for wins lookup. • next server - the ip address of the next server in the boot process, this is usually a tftp server. In addition, custom options can be specified in order to have the dhcp servers hand out all options supported by the dhcp standard. ...

  • Page 192

    10.4.13.241 00-0c-29-04-f8-3c active(static) 10.4.13.242 00-1e-0b-aa-ae-11 active(static) 10.4.13.243 00-1c-c4-36-6c-c4 inactive(static) 10.4.13.244 00-00-00-00-02-14 inactive(static) 10.4.13.254 00-00-00-00-02-54 inactive(static) 10.4.13.1 00-12-79-3b-dd-45 active 10.4.13.2 00-12-79-c4-06-e7 active...

  • Page 193

    5.3. Static dhcp assignment where the administrator requires a fixed relationship between a client and the assigned ip address, netdefendos allows the assignment of a given ip to a specific mac address. Example 5.3. Setting up static dhcp this example shows how to assign the ip address 192.168.1.1 t...

  • Page 194

    Auto save policy what policy should be used to save the lease database to the disk, possible settings are disabled, reconfshut or reconfshuttimer. Default: reconfshut lease store interval how often, in seconds, the leases database should be saved to disk if dhcpserver_saveleasepolicy is set to recon...

  • Page 195: 5.4. Dhcp Relaying

    5.4. Dhcp relaying the dhcp problem with dhcp, clients send requests to locate the dhcp server(s) using broadcast messages. However, broadcasts are normally only propagated across the local network. This means that the dhcp server and client always need to be on the same physical network. In a large...

  • Page 196

    3. Click ok adding a dhcp relayer called as vlan-to-dhcpserver: 1. Go to system > dhcp > add > dhcp relay 2. Now enter: • name: vlan-to-dhcpserver • action: relay • source interface: ipgrp-dhcp • dhcp server to relay to: ip-dhcp • allowed ip offers from server: all-nets 3. Under the add route tab, c...

  • Page 197

    Max auto routes how many relays that can be active at the same time. Default: 256 auto save policy what policy should be used to save the relay list to the disk, possible settings are disabled, reconfshut, or reconfshuttimer. Default: reconfshut auto save interval how often, in seconds, should the r...

  • Page 198: 5.5. Ip Pools

    5.5. Ip pools overview ip pools are used to offer other subsystems access to a cache of dhcp ip addresses. These addresses are gathered into a pool by internally maintaining a series of dhcp clients (one per ip). The dhcp servers used by a pool can either be external or be dhcp servers defined in ne...

  • Page 199

    Maximum free the maximum number of "free" ips to be kept. Must be equal to or greater than the prefetch parameter. The pool will start releasing (giving back ips to the dhcp server) when the number of free clients exceeds this value. Maximum clients optional setting used to specify the maximum numbe...

  • Page 200

    5.5. Ip pools chapter 5. Dhcp services 200

  • Page 201: 6.1. Access Rules

    Chapter 6. Security mechanisms this chapter describes netdefendos security features. • access rules, page 201 • algs, page 204 • web content filtering, page 251 • anti-virus scanning, page 268 • intrusion detection and prevention, page 274 • denial-of-service attack prevention, page 285 • blacklisti...

  • Page 202

    Vpns provide one means of avoiding spoofing but where a vpn is not an appropriate solution then access rules can provide an anti-spoofing capability by providing an extra filter for source address verification. An access rule can verify that packets arriving at a given interface do not have a source...

  • Page 203

    Problems in case a rule is preventing some other function, such as vpn tunnel establishment, from working properly. Example 6.1. Setting up an access rule a rule is to be defined that ensures no traffic with a source address not within the lannet network is received on the lan interface. Cli gw-worl...

  • Page 204: 6.2. Algs

    6.2. Algs 6.2.1. Overview to complement low-level packet filtering, which only inspects packet headers in protocols such as ip, tcp, udp, and icmp, netdefend firewalls provide application layer gateways (algs) which provide filtering at the higher application osi level. An alg object acts as a media...

  • Page 205: 6.2.2. The Http Alg

    Maximum connection sessions the service associated with an alg has a configurable parameter associated with it called max sessions and the default value varies according to the type of alg. For instance, the default value for the http alg is 1000. This means that a 1000 connections are allowed in to...

  • Page 206

    When specifying urls, as described below. • url whitelisting the opposite to blacklisting, this makes sure certain urls are always allowed. Wildcarding can also be used for these urls, as described below. It is important to note that whitelisting a url means that it cannot be blacklisted and it also...

  • Page 207

    Download will be dropped. If nothing is marked in this mode then no files can be downloaded. Additional filetypes not included by default can be added to the allow/block list however these cannot be subject to content checking meaning that the file extension will be trusted as being correct for the ...

  • Page 208: 6.2.3. The Ftp Alg

    Using wildcards in white and blacklists entries made in the white and blacklists can make use of wildcarding to have a single entry be equivalent to a large number of possible urls. The wildcard character "*" can be used to represent any sequence of characters. For example, the entry *.Some_domain.C...

  • Page 209

    Consider a scenario where an ftp client on the internal network connects through the firewall to an ftp server on the internet. The ip rule is then configured to allow network traffic from the ftp client to port 21 on the ftp server. When active mode is used, netdefendos doesn't know that the ftp se...

  • Page 210

    Anti-virus scanning the netdefendos anti-virus subsystem can be enabled to scan all ftp downloads searching for malicious code. Suspect files can be de dropped or just logged. This feature is common to a number of algs and is described fully in section 6.4, “anti-virus scanning”. Ftp alg with zonede...

  • Page 211

    To make it possible to connect to this server from the internet using the ftp alg, the ftp alg and rules should be configured as follows: web interface a. Define the alg: 1. Go to objects > alg > add > ftp alg 2. Enter name: ftp-inbound 3. Check allow client to use active mode 4. Uncheck allow serve...

  • Page 212

    • name: sat-ftp-inbound • action: sat • service: ftp-inbound 3. For address filter enter: • source interface: any • destination interface: core • source network: all-nets • destination network: wan_ip (assuming the external interface has been defined as this) 4. For sat check translate the destinati...

  • Page 213

    Example 6.3. Protecting ftp clients in this scenario shown below the netdefend firewall is protecting a workstation that will connect to ftp servers on the internet. To make it possible to connect to these servers from the internal network using the ftp alg, the ftp alg and rules should be configure...

  • Page 214: 6.2.4. The Tftp Alg

    Rules (using public ips). The following rule needs to be added to the ip rules if using public ip's; make sure there are no rules disallowing or allowing the same kind of ports/traffic before these rules. The service in use is the ftp-outbound, which should be using the alg definition ftp-outbound a...

  • Page 215: 6.2.5. The Smtp Alg

    Allow/disallow read the tftp get function can be disabled so that files cannot be retrieved by a tftp client. The default value is allow. Allow/disallow write the tftp put function can be disabled so that files cannot be written by a tftp client. The default value is allow. Remove request option spe...

  • Page 216

    This is a very useful feature to have since it is possible to put in a block against either an infected client or an infected server sending large amounts of malware generated emails. Email size limiting a maximum allowable size of email messages can be specified. This feature counts the total amoun...

  • Page 217

    4. Anti-virus scanning (if enabled). As described above, if an address is found on the whitelist then it will not be blocked if it also found on the blacklist. Spam filtering, if it is enabled, is still applied to whitelisted addresses but emails flagged as spam will not be tagged nor dropped, only ...

  • Page 218

    The netdefendos smtp alg does not support all esmtp extensions including pipelining and chunking. The alg therefore removes any unsupported extensions from the supported extension list that is returned to the client by an smtp server behind the netdefend firewall. When an extension is removed, a log...

  • Page 219

    Security issue on the public internet. Unsolicited email, sent out in massive quantities by groups known as spammers, can waste resources, transport malware as well as try to direct the reader to webpages which might exploit browser vulnerabilities. Integral to the netdefendos smtp alg is a spam mod...

  • Page 220

    Weighted sum can then be calculated based on all responses. The administrator can configure one of the following actions based on the sum calculated: 1. Dropped if the sum is greater than or equal to a predefined drop threshold then the email is considered to be definitely spam and is discarded or a...

  • Page 221

    And this is what the email's recipient will see in the summary of their inbox contents. The individual user could then decide to set up their own filters in the local client to deal with such tagged emails, possibly sending it to a separate folder. Adding x-spam information if an email is determined...

  • Page 222

    Allowed through if this happens. Setup summary to set up dnsbl spam filtering in the smtp alg, the following list summarizes the steps: • specify which dnsbl servers are to be used. There can be multiple and they can act both as backups to each other as well as confirmation of a sender's status. • s...

  • Page 223

    The dnsbl cli command provides a means to control and monitor the operation of the spam filtering module. The dnsbl command on its own without options shows the overall status of all algs. If the name of the smtp alg object on which dnsbl spam filtering is enabled is my_smtp_alg then the output woul...

  • Page 224: 6.2.6. The Pop3 Alg

    6.2.6. The pop3 alg pop3 is a mail transfer protocol that differs from smtp in that the transfer of mail is directly from a server to a user's client software. Pop3 alg options key features of the pop3 alg are: block clear text authentication block connections between client and server that send the...

  • Page 225

    Note: traffic shaping will not work with the sip alg any traffic connections that trigger an ip rule with a service object that uses the sip alg cannot be also subject to traffic shaping. Sip components the following components are the logical building blocks for sip communication: user agents these...

  • Page 226

    Maximum sessions per id the number of simultaneous sessions that a single client can be involved with is restricted by this value. The default number is 5. Maximum registration time the maximum time for registration with a sip registrar. The default value is 3600 seconds. Sip signal timeout the maxi...

  • Page 227

    (sometimes described as sip pinholes) for allowing the media data traffic to flow through the netdefend firewall. Tip make sure there are no preceding rules already in the ip rule set disallowing or allowing the same kind of traffic. Sip usage scenarios netdefendos supports a variety of sip usage sc...

  • Page 228

    The sip proxy in the above diagram could alternatively be located remotely across the internet. The proxy should be configured with the record-route feature enabled to insure all sip traffic to and from the office clients will be sent through the sip proxy. This is recommended since the attack surfa...

  • Page 229

    Sends its own ip address as contact information to the sip proxy. Netdefendos registers the client's local contact information and uses this to redirect incoming requests to the user. The alg takes care of the address translations needed. 4. Ensure the clients are correctly configured. The sip proxy...

  • Page 230

    This scenario can be implemented in two ways: • using nat to hide the network topology. • without nat so the network topology is exposed. Solution a - using nat here, the proxy and the local clients are hidden behind the ip address of the netdefend firewall. The setup steps are as follows: 1. Define...

  • Page 231

    If record-route is enabled then the source network for outbound traffic from proxy users can be further restricted in the above rules by using "ip_proxy" as indicated. When an incoming call is received, the sip alg will follow the sat rule and forward the sip request to the proxy server. The proxy w...

  • Page 232

    The exchanges illustrated are as follows: • 1,2 - an initial invite is sent to the outbound local proxy server on the dmz. • 3,4 - the proxy server sends the sip messages towards the destination on the internet. • 5,6 - a remote client or proxy server replies to the local proxy server. • 7,8 - the l...

  • Page 233

    Dmz interface as the contact address. • an allow rule for outbound traffic from the proxy behind the dmz interface to the remote clients on the internet. • an allow rule for inbound sip traffic from the sip proxy behind the dmz interface to the ip address of the netdefend firewall. This rule will ha...

  • Page 234: 6.2.8. The H.323 Alg

    • destination port set to 5060 (the default sip signalling port) • type set to tcp/udp 3. Define four rules in the ip rule set: • an allow rule for outbound traffic from the clients on the internal network to the proxy located on the dmz interface. • an allow rule for outbound traffic from the proxy...

  • Page 235

    Gateways an h.323 gateway connects two dissimilar networks and translates traffic between them. It provides connectivity between h.323 networks and non-h.323 networks such as public switched telephone networks (pstn), translating protocols and converting media streams. A gateway is not required for ...

  • Page 236

    • the h.323 alg supports version 5 of the h.323 specification. This specification is built upon h.225.0 v5 and h.245 v10. • in addition to support voice and video calls, the h.323 alg supports application sharing over the t.120 protocol. T.120 uses tcp to transport data while voice and video is tran...

  • Page 237

    Web interface outgoing rule: 1. Go to rules > ip rules > add > iprule 2. Now enter: • name: h323allowout • action: allow • service: h323 • source interface: lan • destination interface: any • source network: lannet • destination network: 0.0.0.0/0 (all-nets) • comment: allow outgoing calls 3. Click ...

  • Page 238

    Example 6.5. H.323 with private ip addresses in this scenario a h.323 phone is connected to the netdefend firewall on a network with private ip addresses. To make it possible to place a call from this phone to another h.323 phone on the internet, and to allow h.323 phones on the internet to call thi...

  • Page 239

    • destination interface: core • source network: 0.0.0.0/0 (all-nets) • destination network: wan_ip (external ip of the firewall) • comment: allow incoming calls to h.323 phone at ip-phone 3. Click ok to place a call to the phone behind the netdefend firewall, place a call to the external ip address ...

  • Page 240

    Incoming rule: 1. Go to rules > ip rules > add > iprule 2. Now enter: • name: h323allowin • action: allow • service: h323 • source interface: any • destination interface: lan • source network: 0.0.0.0/0 (all-nets) • destination network: lannet • comment: allow incoming calls 3. Click ok example 6.7....

  • Page 241

    • source interface: any • destination interface: core • source network: 0.0.0.0/0 (all-nets) • destination network: wan_ip (external ip of the firewall) • comment: allow incoming calls to h.323 phone at ip-phone 3. For sat enter translate destination ip address: to new ip address: ip-phone (ip addre...

  • Page 242

    Web interface incoming gatekeeper rules: 1. Go to rules > ip rules > add > iprule 2. Now enter: • name: h323in • action: sat • service: h323-gatekeeper • source interface: any • destination interface: core • source network: 0.0.0.0/0 (all-nets) • destination network: wan_ip (external ip of the firew...

  • Page 243

    2. Now enter: • name: h323in • action: allow • service: h323-gatekeeper • source interface: lan • destination interface: dmz • source network: lannet • destination network: ip-gatekeeper (ip address of the gatekeeper) • comment: allow incoming communication with the gatekeeper 3. Click ok note: outg...

  • Page 244

    • name: h323out • action: nat • service: h323-gatekeeper • source interface: lan • destination interface: any • source network: lannet • destination network: 0.0.0.0/0 (all-nets) • comment: allow outgoing communication with a gatekeeper 3. Click ok note: outgoing calls do not need a specific rule th...

  • Page 245

    The head office has placed a h.323 gatekeeper in the dmz of the corporate netdefend firewall. This firewall should be configured as follows: web interface 1. Go to rules > ip rules > add > iprule 2. Now enter: • name: lantogk • action: allow • service: h323-gatekeeper • source interface: lan • desti...

  • Page 246

    • source interface: lan • destination interface: dmz • source network: lannet • destination network: ip-gateway • comment: allow h.323 entities on lannet to call phones connected to the h.323 gateway on the dmz 3. Click ok 1. Go to rules > ip rules > add > iprule 2. Now enter: • name: gwtolan • acti...

  • Page 247

    3. Click ok example 6.11. Configuring remote offices for h.323 if the branch and remote office h.323 phones and applications are to be configured to use the h.323 gatekeeper at the head office, the netdefend firewalls in the remote and branch offices should be configured as follows: (this rule shoul...

  • Page 248: 6.2.9. The Tls Alg

    The communication between "external" phones and the gatekeeper to make sure that it is possible for internal phones to call the external phones that are registered with the gatekeeper. 6.2.9. The tls alg overview transport layer security (tls) is a protocol that provides secure communications over t...

  • Page 249

    Advantages of using netdefendos for tls termination tls can be implemented directly in the server to which clients connect, however, if the servers are protected behind a netdefend firewall, then netdefendos can take on the role of the tls endpoint. Netdefendos then performs tls authentication, encr...

  • Page 250

    6. Optionally, a sat rule can be created to change the destination port for the unencrypted traffic. Alternatively an slb_sat rule can be used to do load balancing (the destination port can also be changed through a custom service object). Urls delivered by servers it should be noted that using netd...

  • Page 251: 6.3.1. Overview

    6.3. Web content filtering 6.3.1. Overview web traffic is one of the biggest sources for security issues and misuse of the internet. Inappropriate surfing habits can expose a network to many security threats as well as legal and regulatory liabilities. Productivity and internet bandwidth can also be...

  • Page 252

    Removing such legitimate code could, at best, cause the web site to look distorted, at worst, cause it to not work in a browser at all. Active content handling should therefore only be used when the consequences are well understood. Example 6.13. Stripping activex and java applets this example shows...

  • Page 253

    */*.Gif good. This will block all files with .Gif as the file name extension. Www.Example.Com bad. This will only block the first request to the web site. Surfing to www.Example.Com/index.Html, for example, will not be blocked. *example.Com/* bad. This will also cause www.Myexample.Com to be blocked...

  • Page 254

    7. Click ok finally, make an exception from the blacklist by creating a whitelist: 1. Go to objects > alg 2. In the table, click on the recently created http alg to view its properties 3. Click the http url tab 4. Now click add and select http alg url from the menu 5. Select whitelist as the action ...

  • Page 255

    Figure 6.6. Dynamic content filtering flow if the requested web page url is not present in the databases, then the webpage content at the url will automatically be downloaded to d-link's central data warehouse and automatically analyzed using a combination of software techniques. Once categorized, t...

  • Page 256

    Dynamic content filtering is a feature that is enabled by taking out a separate subscription to the service. This is an addition to the normal netdefendos license. Once a subscription is taken out, an http application layer gateway (alg) object should be defined with dynamic content filtering enable...

  • Page 257

    5. In the blocked categories list, select search sites and click the >> button. 6. Click ok then, create a service object using the new http alg: 1. Go to local objects > services > add > tcp/udp service 2. Specify a suitable name for the service, for example http_content_filtering 3. Select the tcp...

  • Page 258

    This example is based on the same scenario as the previous example, but now with audit mode enabled. Cli first, create an http application layer gateway (alg) object: gw-world:/> add alg alg_http content_filtering webcontentfilteringmode=audit filteringcategories=search_sites web interface first, cr...

  • Page 259

    Will include a dropdown list containing all available categories. If the user believes the requested web site is wrongly classified, he can select a more appropriate category from the dropdown list and submit that as a proposal. The url to the requested web site as well as the proposed category will...

  • Page 260

    This are web sites that contain information relating to sexuality and sexual health, which may be classified under the health sites category (21). Examples might be: • www.Naughtychix.Com • www.Fullonxxx.Com category 2: news a web site may be classified under the news category if its content include...

  • Page 261

    A web site may be classified under the shopping category if its content includes any form of advertisement of goods or services to be exchanged for money, and may also include the facilities to perform that transaction online. Included in this category are market promotions, catalogue selling and me...

  • Page 262

    A web site may be classified under the investment sites category if its content includes information, services or facilities pertaining to personal investment. Urls in this category include contents such as brokerage services, online portfolio setup, money management forums or stock quotes. This cat...

  • Page 263

    • www.Sportstoday.Com • www.Soccerball.Com category 17: www-email sites a web site may be classified under the www-email sites category if its content includes online, web-based email facilities. Examples might be: • www.Coldmail.Com • mail.Yazoo.Com category 18: violence / undesirable a web site ma...

  • Page 264

    Category 22: clubs and societies a web site may be classified under the clubs and societies category if its content includes information or services of relating to a club or society. This includes team or conference web sites. Examples might be: • www.Sierra.Org • www.Walkingclub.Org category 23: mu...

  • Page 265

    • www.Admessages.Com • www.Tripleclick.Com category 28: drugs/alcohol a web site may be classified under the drugs/alcohol category if its content includes drug and alcohol related information or services. Some urls categorized under this category may also be categorized under the health category. E...

  • Page 266

    Particular installation's needs. The webui provides a simple way to download, edit and upload these files. The available files are: compressionforbidden contentforbidden urlforbidden restrictedsitenotice reclassifyurl to perform customization it is necessary to first create a new, named alg banner f...

  • Page 267

    2. A new alg banner files object must exist which the edited file(s) is uploaded to. If the object is called mytxt, the cli command to create this object is: gw-world:/> add httpalgbanners mytxt this creates an object which contains a copy of all the default content filtering banner files. 3. The mo...

  • Page 268: 6.4. Anti-Virus Scanning

    6.4. Anti-virus scanning 6.4.1. Overview the netdefendos anti-virus module protects against malicious code carried in file downloads. Files may be downloaded as part of a web-page in an http transfer, in an ftp download, or perhaps as an attachment to an email delivered through smtp. Malicious code ...

  • Page 269

    Types of file downloads scanned as described above, anti-virus scanning is enabled on a per alg basis and can scan file downloads associated with the http, ftp, smtp and pop3 algs. More specifically: • any uncompressed file type transferred through these algs can be scanned. • if the download has be...

  • Page 270: 6.4.6. Anti-Virus Options

    6.4.4. The signature database safestream netdefendos anti-virus scanning is implemented by d-link using the "safestream" virus signature database. The safestream database is created and maintained by kaspersky, a company which is a world leader in the field of virus detection. The database provides ...

  • Page 271

    3. Compression ratio limit when scanning compressed files, netdefendos must apply decompression to examine the file's contents. Some types of data can result in very high compression ratios where the compressed file is a small fraction of the original uncompressed file size. This can mean that a com...

  • Page 272

    4. When the update is completed, the newly active unit also downloads the files for the update and performs a reconfiguration. 5. This second reconfiguration causes another failover so the passive unit reverts back to being active again. These steps result in both netdefend firewalls in a cluster ha...

  • Page 273

    1. Go to objects > alg > add > http alg 2. Specify a suitable name for the alg, for instance anti_virus 3. Click the antivirus tab 4. Select protect in the mode dropdown list 5. Click ok b. Then, create a service object using the new http alg: 1. Go to local objects > services > add > tcp/udp servic...

  • Page 274: 6.5.1. Overview

    6.5. Intrusion detection and prevention 6.5.1. Overview intrusion definition computer servers can sometimes have vulnerabilities which leave them exposed to attacks carried by network traffic. Worms, trojans and backdoor exploits are examples of such attacks which, if successful, can potentially com...

  • Page 275

    • maintenance idp maintenance idp is the base idp system included as standard with the netdefend dfl 210, 800, 1600 and 2500. Maintenance idp is a simplified idp that gives basic protection against idp attacks. It is upgradeable to the higher level and more comprehensive advanced idp which is discus...

  • Page 276: 6.5.3. Idp Rules

    Configurable interval. This is done via an http connection to the d-link server network which delivers the latest signature database updates. If the server's signature database has a newer version than the current local database, the new database will be downloaded, replacing the older version. The ...

  • Page 277

    Each idp rule has a section of settings for http normalization. This allows the administrator to choose the actions that should be taken when idp finds inconsistencies in the uris embedded in incoming http requests. Some server attacks are based on creating uris with sequences that can exploit weakn...

  • Page 278

    Insertion attacks an insertion attack consists of inserting data into a stream so that the resulting sequence of data packets is accepted by the idp subsystem but will be rejected by the targeted application. This results is two different streams of data. As an example, consider a data stream broken...

  • Page 279

    In order for idp to correctly identify an attack, it uses a profile of indicators, or pattern, associated with different types of attack. These predefined patterns, also known as signatures, are stored in a local netdefendos database and are used by the idp module to analyze traffic for attack patte...

  • Page 280

    Idp signature groups fall into a three level hierarchical structure. The top level of this hierarchy is the signature type, the second level the category and the third level the sub-category. The signature group called policy_db_mssql illustrates this principle where policy is the type, db is the ca...

  • Page 281: 6.5.7. Idp Actions

    Scanning can make the load on the firewall hardware unnecessarily high, adversely affecting throughput. 6.5.7. Idp actions action options after pattern matching recognizes an intrusion in traffic subject to an idp rule, the action associated with that rule is taken. The administrator can associate o...

  • Page 282

    Wait 600 seconds (equivalent to 10 minutes) before sending a new email. An smtp server is assumed to have been configured in the address book with the name smtp-server. Cli adding an smtp log receiver: gw-world:/> add logreceiver logreceiversmtp smt4idp ipaddress=smtp-server receiver1=youremail@your...

  • Page 283

    An idp rule called idpmailsrvrule will be created, and the service to use is the smtp service. Source interface and source network defines where traffic is coming from, in this example the external network. The destination interface and destination network define where traffic is directed to, in thi...

  • Page 284

    Specify the action: an action is now defined, specifying what signatures the idp should use when scanning data matching the rule, and what netdefendos should do when a possible intrusion is detected. In this example, intrusion attempts will cause the connection to be dropped, so action is set to pro...

  • Page 285: 6.6.1. Overview

    6.6. Denial-of-service attack prevention 6.6.1. Overview by embracing the internet, enterprises experience new business opportunities and growth. The enterprise network and the applications that run over it are business critical. Not only can a company reach a larger number of customers via the inte...

  • Page 286: Boink And Nestea

    Intended victim. "jolt" is simply a purpose-written program for generating such packets on operating systems whose ping commands refuse to generate oversized packets. The triggering factor is that the last fragment makes the total packet size exceed 65535 bytes, which is the highest number that a 16...

  • Page 287

    • by stripping the urg bit by default from all tcp segments traversing the system (configurable via advanced settings > tcp > tcpurg). Winnuke attacks will usually show up in netdefendos logs as normal drops with the name of the rule in your policy that disallowed the connection attempt. For connect...

  • Page 288: 6.6.9. The Jolt2 Attack

    6.6.8. Tcp syn flood attacks the tcp syn flood attack works by sending large amounts of tcp syn packets to a given port and then not responding to syn acks sent in response. This will tie up local tcp stack resources on the victim machine until it is unable to respond to more syn packets until the e...

  • Page 289

    6.7. Blacklisting hosts and networks overview netdefendos implements a blacklist of host or network ip addresses which can be utilized to protect against traffic coming from specific internet sources. Certain netdefendos subsystems have the ability to optionally blacklist a host or network when cert...

  • Page 290

    Blacklisted, it still does not prevent netdefendos mechanisms such as threshold rules from dropping or denying connections from that source. What whitelisting does is prevent a source being added to a blacklist if that is the action a rule has specified. For further details on usage see section 6.5....

  • Page 291

    6.7. Blacklisting hosts and networks chapter 6. Security mechanisms 291.

  • Page 292: 7.1. Nat

    Chapter 7. Address translation this chapter describes netdefendos address translation capabilities. • nat, page 292 • nat pools, page 297 • sat, page 300 the ability of netdefendos to change the ip address of packets as they pass through the netdefend firewall is known as address translation. The ab...

  • Page 293

    Nat provides many-to-one translation. This means that each nat rule in the ip rule set will translate between several source ip addresses and a single source ip address. To maintain session state information, each connection from dynamically translated addresses uses a unique port number and ip addr...

  • Page 294

    Many nat pools and a single pool can be used in more than one nat rule. This topic is discussed further in section 7.2, “nat pools”. Applying nat translation the following illustrates how nat is applied in practice on a new connection: 1. The sender, for example 192.168.1.5, sends a packet from a dy...

  • Page 295

    1. Go to rules > ip rules > add > iprule 2. Specify a suitable name for the rule, for example nat_http 3. Now enter: • action: nat • service: http • source interface: lan • source network: lannet • destination interface: any • destination network: all-nets 4. Under the nat tab, make sure that the us...

  • Page 296

    We shall examine the typical case where the netdefend firewall acts as a pptp server and terminates the pptp tunnel for pptp clients. Clients that wish to be anonymous, communicate with their local isp using pptp. The traffic is directed to the anonymizing service provider where a netdefend firewall...

  • Page 297: 7.2. Nat Pools

    7.2. Nat pools overview as discussed in section 7.1, “nat”, nat provides a way to have multiple internal clients and hosts with unique private internal ip addresses communicate to remote hosts through a single external public ip address. When multiple public external ip addresses are available then ...

  • Page 298

    Stateless nat pools the stateless option means that no state table is maintained and the external ip address chosen for each new connection is the one that has the least connections already allocated to it. This means two connections between one internal host to the same external host may use two di...

  • Page 299

    Web interface a. First create an object in the address book for the address range: 1. Go to objects > address book > add > ip address 2. Specify a suitable name for the ip range nat_pool_range 3. Enter 10.6.13.10-10.16.13.15 in the ip address textbox (a network such as 10.6.13.0/24 could be used her...

  • Page 300: 7.3. Sat

    7.3. Sat netdefendos can translate entire ranges of ip addresses and/or ports. Such translations are transpositions, each address or port is mapped to a corresponding address or port in the new range, rather than translating them all to the same address or port. In netdefendos this functionality is ...

  • Page 301

    Destinationnetwork=wan_ip sattranslate=destinationip sattranslatetoip=10.10.10.5 name=sat_http_to_dmz then create a corresponding allow rule: gw-world:/main> add iprule action=allow service=http sourceinterface=any sourcenetwork=all-nets destinationinterface=core destinationnetwork=wan_ip name=allow...

  • Page 302

    Hide: # action src iface src net dest iface dest net parameters 3 nat lan lannet any all-nets all now, what is wrong with this rule set? If we assume that we want to implement address translation for reasons of security as well as functionality, we discover that this rule set makes our internal addr...

  • Page 303

    # action src iface src net dest iface dest net parameters 1 sat any all-nets core wan_ip http setdest wwwsrv 80 2 allow any all-nets core wan_ip http these two rules allow us to access the web server via the netdefend firewall's external ip address. Rule 1 states that address translation can take pl...

  • Page 304

    In this way, the reply arrives at pc1 from the expected address. Another possible solution to this problem is to allow internal clients to speak directly to 10.0.0.2 and this would completely avoid all the problems associated with address translation. However, this is not always practical. 7.3.2. Tr...

  • Page 305

    Gw-world:/> add address ip4address wwwsrv_priv_base address=10.10.10.5 publish the public ip addresses on the wan interface using arp publish. One arp item is needed for every ip address: gw-world:/> add arp interface=wan ip=195.55.66.77 mode=publish repeat this for all the five public ip addresses....

  • Page 306: 7.3.4. Port Translation

    • servce: http • source interface:any • source network: all-nets • destination interface: wan • destination network: wwwsrv_pub 4. Switch to the sat tab 5. Make sure that the destination ip address option is selected 6. In the new ip address dropdown list, select wwwsrv_priv 7. Click ok finally, cre...

  • Page 307

    # action src iface src net dest iface dest net parameters 1 sat any all-nets wan wwwsrv_pub tcp 80-85 setdest 192.168.0.50 1080 this rule produces a 1:1 translation of all ports in the range 80 - 85 to the range 1080 - 1085. • attempts to communicate with the web servers public address - port 80, wi...

  • Page 308

    If anyone tries to connect to the public address of the web server, the destination address will be changed to its private address. # action src iface src net dest iface dest net parameters 1 sat lan lannet wwwsrv_pub tcp 80-85 setdest intrasrv 1080 2 sat any all-nets wwwsrv_pub tcp 80-85 setdest ww...

  • Page 309

    • return traffic from wwwsrv:80 will match rules 2 and 3. The replies will therefore be dynamically address translated. This changes the source port to a completely different port, which will not work. The problem can be solved using the following rule set: # action src iface src net dest iface dest...

  • Page 310

    7.3.7. Sat and fwdfast rules chapter 7. Address translation 310

  • Page 311: 8.1. Overview

    Chapter 8. User authentication this chapter describes how netdefendos implements user authentication. • overview, page 311 • authentication setup, page 313 • customizing html pages, page 325 8.1. Overview in situations where individual users connect to protected resources through the netdefend firew...

  • Page 312

    • changed on a regular basis such as every three months. 8.1. Overview chapter 8. User authentication 312.

  • Page 313: 8.2. Authentication Setup

    8.2. Authentication setup 8.2.1. Setup summary the following list summarizes the steps for user authentication setup with netdefendos: • set up a database of users, each with a username/password combination. This can exist locally in a netdefendos user db object, or remotely on a radius server and w...

  • Page 314

    Radius with netdefendos netdefendos acts as a radius client, sending user credentials and connection parameter information as a radius message to a nominated radius server. The server processes the requests and sends back a radius message to accept or deny them. One or more external servers can be d...

  • Page 315

    Unreachable. The default value for this setting is 5. • name attribute the name of the field in the ldap server containing the username. The default value is uid. This should be set to samaccountname if using active directory. • retrieve group membership if this option is enabled, group memberships ...

  • Page 316

    Ldap server authentication is automatically configured to work using ldap bind request authentication. This means that authentication succeeds if successful connection is made to the ldap server. Individual clients are not distinguished from one another. Ldap server referrals should not occur with b...

  • Page 317

    Command: gw-world:/> show ldapdatabase the entire contents of the database can be displayed with the command: gw-world:/> show ldapdatabase ldap authentication and ppp when using a ppp based client for pptp or l2tp access, special consideration has to be taken if ldap authentication is to succeed wi...

  • Page 318

    Compare with the digest sent by the client. A successful digest match then results in successful authentication. The essential difference with the normal event sequence in a above is that it is the netdefend firewall itself which is performing the authentication. Figure 8.2. Ldap for ppp with chap, ...

  • Page 319

    • the local database defined within netdefendos. • a radius server (discussed below). • an external ldap server database (discussed below). A further option, disallow, can be used so that a negative rule can be created which says "never authenticate given these conditions". This option might be used...

  • Page 320: 8.2.7. Http Authentication

    8.2.6. Authentication processing the list below describes the processing flow through netdefendos for username/password authentication: 1. A user creates a new connection to the netdefend firewall. 2. Netdefendos sees the new user connection on an interface and checks the authentication rule set to ...

  • Page 321

    Options. These are: • login type - this can be one of: • form - the user is presented with an html page for authentication which is filled in and the data sent back to netdefendos with a post. • basicauth - this sends a 401 - authentication required message back to the browser which will cause it to...

  • Page 322

    The sat rule catches all unauthenticated requests and must be set up with an all-to-one address mapping that directs them to the address 127.0.0.1 which corresponds to core (netdefendos itself). 8.2.7. Http authentication chapter 8. User authentication 322.

  • Page 323

    Example 8.1. Creating an authentication user group in the example of an authentication address object in the address book, a user group "users" is used to enable user authentication on "lannet". This example shows how to configure the user group in the netdefendos database. Web interface step a 1. G...

  • Page 324

    • destination network lan_ip 3. Click ok b. Set up the authentication rule 1. Go to user authentication > user authentication rules > add > user authentication rule 2. Now enter: • name: httplogin • agent: http • authentication source: local • interface: lan • originator ip: lannet 3. For local user...

  • Page 325

    F. Shared secret: enter a text string here for basic encryption of the radius messages g. Confirm secret: retype the string to confirm the one typed above 3. Click ok 8.3. Customizing html pages user authentication makes use of a set of html files to present information to the user during the authen...

  • Page 326

    • %ipaddr% - the ip address which is being browsed from. • %reason% - the reason that access was denied. • - the web page url for redirects. The %redirurl% parameter in certain banner web pages, the parameter %redirurl% appears. This is a placeholder for the original url which was requested before t...

  • Page 327

    2. A new auth banner files object must exist which the edited file(s) is uploaded to. If the object is called ua_html, the cli command to create this object is: gw-world:/> add httpauthbanners ua_html this creates an object which contains a copy of all the default user auth banner files. 3. The modi...

  • Page 328

    8.3. Customizing html pages chapter 8. User authentication 328.

  • Page 329: Chapter 9. Vpn

    Chapter 9. Vpn this chapter describes the virtual private network (vpn) functionality in netdefendos. • overview, page 329 • vpn quick start, page 333 • ipsec components, page 343 • ipsec tunnels, page 357 • pptp/l2tp, page 375 • ca server access, page 383 • vpn troubleshooting, page 386 9.1. Overvi...

  • Page 330: 9.1.2. Vpn Encryption

    2. Client to lan connection - where many remote clients need to connect to an internal network over the internet. In this case, the internal network is protected by the netdefend firewall to which the client connects and the vpn tunnel is set up between them. 9.1.2. Vpn encryption encryption of vpn ...

  • Page 331: 9.1.4. Key Distribution

    • restricting access through the vpn to needed services only, since mobile computers are vulnerable. • creating dmzs for services that need to be shared with other companies through vpns. • adapting vpn access policies for different groups of users. • creating key distribution policies. Endpoint sec...

  • Page 332

    “the tls alg”. 9.1.5. The tls alternative for vpn chapter 9. Vpn 332.

  • Page 333: 9.2. Vpn Quick Start

    9.2. Vpn quick start overview later sections in this chapter will explore vpn components in detail. To help put those later sections in context, this section is a quick start summary of the steps needed for vpn setup. It outlines the individual steps in setting up vpns for the most common scenarios....

  • Page 334

    9.2.1. Ipsec lan to lan with pre-shared keys 1. Create a pre-shared key object. 2. Optionally create a new ike algorithms object and/or an ipsec algorithms object if the default algorithm proposal lists do not provide a set of algorithms that are acceptable to the tunnel remote end point. This will ...

  • Page 335

    Action src interface src network dest interface dest network service allow ipsec_tunnel remote_net lan lannet all the service used in these rules is all but it could be a predefined service. 6. Define a new netdefendos route which specifies that the vpn tunnel ipsec_tunnel is the interface to use fo...

  • Page 336

    Considered adequate. Two self-signed certificates are required and the same two are used at either end of the tunnel but their usage is reversed. In other words: one certificate is used as the root certificate at one end, call it side a, and as the host certificate at the other end, call it side b. ...

  • Page 337

    The group string for a user can be specified if its group's access is to be restricted to certain source networks. Group can be specified (with the same text string) in the authentication section of an ip object. If that ip object is then used as the source network of a rule in the ip rule set, that...

  • Page 338

    • create a config mode pool object (there can only be one associated with a netdefendos installation) and in it specify the address range. • enable the ike config mode option in the ipsec tunnel object ipsec_tunnel. 2. If client ip addresses are to be retrieved through dhcp: • create an ip pool obje...

  • Page 339

    Note: the system time and date should be correct the netdefendos date and time should be set correctly since certificates have an expiry date and time. Also review section 9.6, “ca server access”, which describes important considerations for certificate validation. 9.2.5. L2tp roaming clients with p...

  • Page 340

    • set outer interface filter to ipsec_tunnel. • set outer server ip to ip_ext. • select the microsoft point-to-point encryption allowed. Since ipsec encryption is used this can be set to be none only, otherwise double encryption will degrade throughput. • set ip pool to l2tp_pool. • enable proxy arp...

  • Page 341

    2. Load a gateway certificate and root certificate into netdefendos. 3. When setting up the ipsec tunnel object, specify the certificates to use under authentication. This is done by: a. Enable the x.509 certificate option. B. Select the gateway certificate. C. Add the root certificate to use. 4. If...

  • Page 342

    3. Define a user authentication rule, this is almost identical to l2tp: agent auth source src network interface client source ip ppp local all-nets pptp_tunnel all-nets (0.0.0.0/0) 4. Now set up the ip rules in the ip rule set: action src interface src network dest interface dest network service all...

  • Page 343: 9.3. Ipsec Components

    9.3. Ipsec components 9.3.1. Overview internet protocol security (ipsec) is a set of protocols defined by the internet engineering task force (ietf) to provide ip security at the network layer. An ipsec based vpn is made up of two parts: • internet key exchange protocol (ike) • ipsec protocols (ah/e...

  • Page 344

    Describing the incoming traffic, and the other the outgoing. In cases where esp and ah are used in conjunction, four sas will be created. Ike negotiation the process of negotiating session parameters consists of a number of phases and modes. These are described in detail in the below sections. The f...

  • Page 345

    However, since we do not want to publish to much of the negotiation in plaintext, we first agree upon a way of protecting the rest of the ike negotiation. This is done, as described in the previous section, by the initiator sending a proposal-list to the responder. When this has been done, and the r...

  • Page 346

    This way, an eavesdropper will only see encrypted traffic going from one of vpn endpoint to another. In transport mode, the traffic will not be tunneled, and is hence not applicable to vpn tunnels. It can be used to secure a connection from a vpn client directly to the netdefend firewall, for exampl...

  • Page 347

    Ike encryption this specifies the encryption algorithm used in the ike negotiation, and depending on the algorithm, the size of the encryption key used. The algorithms supported by netdefendos ipsec are: • aes • blowfish • twofish • cast128 • 3des • des des is only included to be interoperable with ...

  • Page 348

    Pfs dh group this specifies the diffie-hellman group to use with pfs. The available dh groups are discussed below. Ipsec dh group this specifies the diffie-hellman group to use for ipsec communication. The available dh groups are discussed below in the section titled diffie-hellman groups. Ipsec enc...

  • Page 349: 9.3.3. Ike Authentication

    By netdefendos are as follows: • dh group 1 (768-bit) • dh group 2 (1024-bit) • dh group 5 (1536-bit) all these ha groups are available for use with ike, ipsec and pfs. 9.3.3. Ike authentication manual keying the "simplest" way of configuring a vpn is by using a method called manual keying. This is ...

  • Page 350

    One thing that has to be considered when using pre-shared keys is key distribution. How are the pre-shared keys distributed to remote vpn clients and firewalls? This is a major issue, since the security of a psk system is based on the psks being secret. Should one psk be compromised, the configurati...

  • Page 351: 9.3.5. Nat Traversal

    Ah uses a cryptographic hash function to produce a mac from the data in the ip packet. This mac is then transmitted with the packet, allowing the remote endpoint to verify the integrity of the original ip packet, making sure the data has not been tampered with on its way through the internet. Apart ...

  • Page 352

    Achieving nat detection to achieve nat detection both ipsec peers send hashes of their own ip addresses along with the source udp port used in the ike negotiations. This information is used to see whether the ip address and source port each peer uses is the same as what the other peer sees. If the s...

  • Page 353

    There are two types of proposal lists, ike proposal lists and ipsec proposal lists. Ike lists are used during ike phase-1 (ike security negotiation), while ipsec lists are using during ike phase-2 (ipsec security negotiation). Several algorithm proposal lists are already defined by default in netdef...

  • Page 354: 9.3.7. Pre-Shared Keys

    9.3.7. Pre-shared keys pre-shared keys are used to authenticate vpn tunnels. The keys are secrets that are shared by the communicating parties before communication takes place. To communicate, both parties prove that they know the secret. The security of a shared secret depends on how "good" a passp...

  • Page 355

    9.3.8. Identification lists when certificates are used as authentication method for ipsec tunnels, the netdefend firewall will accept all remote devices or vpn clients that are capable of presenting a certificate signed by any of the trusted certificate authorities. This can be a potential problem, ...

  • Page 356

    1. Go to objects > vpn objects > id list > add > id list 2. Enter a name for the list, for example myidlist 3. Click ok then, create an id: 1. Go to objects > vpn objects > ike id list > add > id list 2. Select myidlist 3. Enter a name for the id, for example johndoe 4. Select distinguished name in ...

  • Page 357: 9.4. Ipsec Tunnels

    9.4. Ipsec tunnels 9.4.1. Overview an ipsec tunnel defines an endpoint of an encrypted tunnel. Each ipsec tunnel is interpreted as a logical interface by netdefendos, with the same filtering, traffic shaping and configuration capabilities as regular interfaces. Remote initiation of tunnel establishm...

  • Page 358: 9.4.3. Roaming Clients

    Ipsec tunnel quick start this section covers ipsec tunnels in some detail. A quick start checklist of setup steps for these protocols in typical scenarios can be found in the following sections: • section 9.2.1, “ipsec lan to lan with pre-shared keys”. • section 9.2.2, “ipsec lan to lan with certifi...

  • Page 359

    The algorithm proposal lists that are pre-configured in netdefendos. 9.4.3.1. Psk based client tunnels example 9.4. Setting up a psk based vpn tunnel for roaming clients this example describes how to configure an ipsec tunnel at the head office netdefend firewall for roaming clients that connect to ...

  • Page 360

    Clients that connect to the office to gain remote access. The head office network uses the 10.0.1.0/24 network span with external firewall ip wan_ip. Web interface a. Create a self-signed certificate for ipsec authentication: the step to actually create self-signed certificates is performed outside ...

  • Page 361

    E. Finally configure the ip rule set to allow traffic inside the tunnel. 9.4.3.3. Tunnels based on ca server certificates setting up client tunnels using a ca issued certificate is largely the same as using self-signed certificates with the exception of a couple of steps. Most importantly, it is the...

  • Page 362

    • encapsulation mode: tunnel 3. For algorithms enter: • ike algorithms: medium or high • ipsec algorithms: medium or high 4. For authentication enter: • choose x.509 certificates as the authentication method • root certificate(s): select your ca server root certificate imported earlier and add it to...

  • Page 363

    Example 9.7. Setting up config mode in this example, the config mode pool object is enabled by associating with it an already configured ip pool object called ip_pool1. Web interface 1. Go to objects > vpn objects > ike config mode pool 2. The config mode pool object properties web page now appears ...

  • Page 364

    This example shows how to manually setup and specify an ldap server. Cli gw-world:/> add ldapserver host=192.168.101.146 username=myusername password=mypassword port=389 web interface 1. Go to objects > vpn objects > ldap > add > ldap server 2. Now enter: • ip address: 192.168.101.146 • username: my...

  • Page 365

    Complete ikesnoop command options can be found in the cli reference guide. The client and the server the two parties involved in the tunnel negotiation are referred to in this section as the client and server. In this context, the word "client" is used to refer to the device which is the initiator o...

  • Page 366

    Life type : kilobytes life duration : 50000 transform 4/4 transform id : ike encryption algorithm : 3des-cbc hash algorithm : sha authentication method : pre-shared key group description : modp 1024 life type : seconds life duration : 43200 life type : kilobytes life duration : 50000 vid (vendor id)...

  • Page 367

    Ikesnoop: sending ike packet to 192.168.0.10:500 exchange type : identity protection (main mode) isakmp version : 1.0 flags : cookies : 0x6098238b67d97ea6 -> 0x5e347cb76e95a message id : 0x00000000 packet length : 224 bytes # payloads : 8 payloads: sa (security association) payload data length : 52 ...

  • Page 368

    Packet length : 220 bytes # payloads : 4 payloads: ke (key exchange) payload data length : 128 bytes nonce (nonce) payload data length : 16 bytes nat-d (nat detection) payload data length : 16 bytes nat-d (nat detection) payload data length : 16 bytes step 4. Server sends key exchange data the serve...

  • Page 369

    Explanation of above values flags: e means encryption (it is the only flag used). Id: identification of the client the notification field is given as initial contact to indicate this is not a re-key. Step 6. Server id response the server now responds with its own id. Ikesnoop: sending ike packet to ...

  • Page 370

    Transform id : rijndael (aes) key length : 128 authentication algorithm : hmac-sha-1 sa life type : seconds sa life duration : 21600 sa life type : kilobytes sa life duration : 50000 encapsulation mode : tunnel transform 3/4 transform id : blowfish key length : 128 authentication algorithm : hmac-md...

  • Page 371

    Packet length : 156 bytes # payloads : 5 payloads: hash (hash) payload data length : 16 bytes sa (security association) payload data length : 56 bytes doi : 1 (ipsec doi) proposal 1/1 protocol 1/1 protocol id : esp spi size : 4 spi value : 0xafba2d15 transform 1/1 transform id : rijndael (aes) key l...

  • Page 372

    Tunnels if the latter is changed. This linkage is broken once ipsec max rules is altered manually so that subsequent changes to ipsec max tunnels will not cause an automatic change in ipsec max rules. Default: 4 times the license limit of ipsec max tunnels ipsec max tunnels specifies the total numbe...

  • Page 373

    When the signature of a user certificate is verified, netdefendos looks at the issuer name field in the user certificate to find the ca certificate the certificate was signed by. The ca certificate may in turn be signed by another ca, which may be signed by another ca, and so on. Each certificate wi...

  • Page 374

    This setting is used with ikev1 only. Default: 2 (in other words, 2 x 10 = 20 seconds) dpd expire time the length of time in seconds for which dpd messages will be sent to the peer. If the peer has not responded to messages during this time it is considered to be dead. In other words, the length of ...

  • Page 375: 9.5. Pptp/l2Tp

    9.5. Pptp/l2tp the access by a client using a modem link over dial-up public switched networks, possibly with an unpredictable ip address, to protected networks via a vpn poses particular problems. Both the pptp and l2tp protocols provide two different means of achieving vpn access from remote clien...

  • Page 376: 9.5.2. L2Tp Servers

    Tcp port 1723 and/or ip protocol 47 before the pptp connection can be made to the netdefend firewall. Examining the log can indicate if this problem occurred, with a log message of the following form appearing: error ppp lcp_negotiation_stalled ppp_terminated example 9.10. Setting up a pptp server t...

  • Page 377

    This example shows how to setup a l2tp network server. The example assumes that you have created some address objects in the address book. You will have to specify the ip address of the l2tp server interface, an outer ip address (that the l2tp server should listen to) and an ip pool that the l2tp se...

  • Page 378

    • username: testuser • password: mypassword • confirm password: mypassword 5. Click ok now we will setup the ipsec tunnel, which will later be used in the l2tp section. As we are going to use l2tp, the local network is the same ip as the ip that the l2tp tunnel will connect to, wan_ip. Furthermore, ...

  • Page 379

    Web interface 1. Go to interfaces > l2tp servers > add > l2tpserver 2. Enter a name for the l2tp tunnel, for example l2tp_tunnel 3. Now enter: • inner ip address: lan_ip • tunnel protocol: l2tp • outer interface filter: l2tp_ipsec • server ip: wan_ip 4. Under the ppp parameters tab, check the use us...

  • Page 380

    Destinationinterface=any destinationnetwork=all-nets name=allowl2tp gw-world:/main> add iprule action=nat service=all_services sourceinterface=l2tp_tunnel sourcenetwork=l2tp_pool destinationinterface=any destinationnetwork=all-nets name=natl2tp web interface 1. Go to rules > ip rules > add > iprule ...

  • Page 381: 9.5.4. Pptp/l2Tp Clients

    Max ppp resends the maximum number of ppp layer resends. Default: 10 9.5.4. Pptp/l2tp clients the pptp and l2tp protocols are described in the previous section. In addition to being able to act as a pptp or l2tp server, netdefendos also offers the ability to act as a pptp or l2tp clients. This can b...

  • Page 382

    If dial on demand is enabled then the pptp/l2tp tunnel will not be set up until traffic is sent on the interface. The parameters for this option are: • activity sense - specifies if dial-on-demand should trigger on send or recv or both. • idle timeout - the time of inactivity in seconds to wait befo...

  • Page 383: 9.6. Ca Server Access

    9.6. Ca server access overview where certificates are used, the two sides of a vpn tunnel exchange their certificates during the tunnel setup negotiation and either may then try to validate the received certificate by accessing a ca server. A certificate contains a url (the crl distribution point) w...

  • Page 384

    3. The ca server is a commercial server on the public internet. In this, the simplest case, public dns servers will resolve the fqdn. The only requirement is that netdefendos will need to have at least one public dns server address configured to resolve the fqdns in the certificates it receives. • i...

  • Page 385

    As explained previously, the address of the private ca server must be resolvable through public dns servers for certificate validation requests coming from the public internet. If the certificate queries are coming only from the netdefend firewall and the ca server is on the internal side of the fir...

  • Page 386: 9.7. Vpn Troubleshooting

    9.7. Vpn troubleshooting general troubleshooting in all types of vpns some basic troubleshooting checks can be made: • check that all ip addresses have been specified correctly. • check that all pre-shared keys and usernames/passwords are correctly entered. • use icmp ping to confirm that the tunnel...

  • Page 387

    • check that the correct certificates have been used. • check that the certificate .Cer and .Key files have the same filename. For example, my_cert.Key and my_cert.Cer. • check that the certificates have not expired. • check that the netdefendos date and time is set correctly and consider time-zone ...

  • Page 388

    Single tunnel by specifying the ip address of the tunnel's endpoint (this is either the ip of the remote endpoint or a client's ip address). The command takes the form: ikesnoop -on -verbose ikesnoop can be turned off with the command: ikesnoop -off for a more detailed discussion of this topic, see ...

  • Page 389

    Management interface failure with vpn chapter 9. Vpn 389.

  • Page 390: 10.1. Traffic Shaping

    Chapter 10. Traffic management this chapter describes how netdefendos can manage network traffic. • traffic shaping, page 390 • idp traffic shaping, page 407 • threshold rules, page 412 • server load balancing, page 414 10.1. Traffic shaping 10.1.1. Introduction qos with tcp/ip a weakness of tcp/ip ...

  • Page 391

    Traffic shaping objectives traffic shaping operates by measuring and queuing ip packets with respect to a number of configurable parameters. The objectives are: • applying bandwidth limits and queuing packets that exceed configured limits, then sending them later when bandwidth demands are lower. • ...

  • Page 392

    Needed in an isp scenario where individual pipes are allocated to each client. Pipe rules pipe rules make up the pipe rule set. Each rule is defined much like other netdefendos policies: by specifying the source/destination interface/network as well as the service to which the rule is to apply. Once...

  • Page 393

    It is important to understand that traffic shaping will not work with connection that are established because of a fwdfast rule in the netdefendos ip rule set. The reason for this is that traffic shaping is implemented based on the netdefendos state engine and a fwdfast ip rule does not set up a con...

  • Page 394

    Pass through the std-in pipe. Cli gw-world:/> add piperule returnchain=std-in sourceinterface=lan sourcenetwork=lannet destinationinterface=wan destinationnetwork=all-nets service=all_services name=outbound web interface 1. Go to traffic management > traffic shaping > add > pipe rule 2. Specify a su...

  • Page 395

    Example 10.2. Limiting bandwidth in both directions create a second pipe for outbound traffic: cli gw-world:/> add pipe std-out limitkbpstotal=2000 web interface 1. Go to traffic management > traffic shaping > pipes > add > pipe 2. Specify a name for the pipe, for example std-out 3. Enter 2000 in to...

  • Page 396: 10.1.6. Precedences

    This is not a bandwidth guarantee for web browsing but it is a 125 kbps bandwidth guarantee for everything except web browsing. For web browsing the normal rules of first-come, first-forwarded will apply when competing for bandwidth. This may mean 125 kbps, but it may also mean much slower speed if ...

  • Page 397

    The minimum and maximum precedences define the precedence range that the pipe will handle. If a packet arrives with an already allocated precedence below the minimum then its precedence is changed to the minimum. Similarly, if a packet arrives with an already allocated precedence above the maximum, ...

  • Page 398: 10.1.7. Guarantees

    Pipe's configuration is exceeded. Lower priority packets will be buffered and sent when higher priority traffic uses less than the maximum specified for the pipe. The buffering process is sometimes referred to as "throttling back" since it reduces the flow rate. The need for guarantees a problem can...

  • Page 399: 10.1.9. Groups

    Keep the forward chain of both rules as std-out only. Again, to simplify this example, we concentrate only on inbound traffic, which is the direction that is the most likely to be the first one to fill up in client-oriented setups. Set the return chain of the port 22 rule to ssh-in followed by std-i...

  • Page 400: 10.1.10. Recommendations

    Computer a is not the same as port 1024 of computer b and individual connections are identifiable. If grouping by network is chosen, the network size should also be specified (this has the same meaning as the netmask). A simple groups scenario if the total bandwidth limit for a pipe is 400 bps and w...

  • Page 401

    Knows what its capacity is and the precedence mechanism is totally dependent on this. Pipe limits for vpn traffic shaping measures the traffic inside vpn tunnels. This is the raw unencrypted data without any protocol overhead so it will be less than the actual vpn traffic. Vpn protocols such as ipse...

  • Page 402

    Consumed by parties outside of administrator control but sharing the same connection. Troubleshooting for a better understanding of what is happening in a live setup, the console command: pipe -u can be used to display a list of currently active users in each pipe. 10.1.11. A summary of traffic shap...

  • Page 403

    The reason for using 2 different pipes in this case, is that these are easier to match to the physical link capacity. This is especially true with asynchronous links such as adsl. First, two pipes called in-pipe and out-pipe need to be created with the following parameters: pipe name min prec def pr...

  • Page 404

    • priority 0 - web plus remaining from other levels to implement this scheme, we can use the in-pipe and out-pipe. We first enter the pipe limits for each pipe. These limits correspond to the list above and are: • priority 6 - 500 • priority 4 - 250 • priority 2 - 1000 now create the pipe rules: rul...

  • Page 405

    The pipe chaining can be used as a solution to the problem of vpn overhead. A limit which allows for this overhead is placed on the vpn tunnel traffic and non-vpn traffic is inserted into a pipe that matches the speed of the physical link. To do this we first create separate pipes for the outgoing t...

  • Page 406

    If sat is being used, for example with a web server or ftp server, that traffic also needs to be forced into pipes or it will escape traffic shaping and ruin the planned quality of service. In addition, server traffic is initiated from the outside so the order of pipes needs to be reversed: the forw...

  • Page 407: 10.2. Idp Traffic Shaping

    10.2. Idp traffic shaping 10.2.1. Overview the idp traffic shaping feature is traffic shaping that is performed based on information coming from the netdefendos intrusion detection and prevention (idp) subsystem (for more information on idp see section 6.5, “intrusion detection and prevention”). The...

  • Page 408: 10.2.3. Processing Flow

    Afterwards when other connections will be opened and subject to traffic shaping. Connections opened after the time window has expired will no longer be subject to traffic shaping. A time window value of 0 means that only traffic flowing over the initial triggering connection will be subject to traff...

  • Page 409: 10.2.5. A P2P Scenario

    Network range but not host x. This tells netdefendos that host x is not relevant in making a decision about including new non-idp-triggering connections in traffic shaping. It may seem counter-intuitive that client b is also included in the network range but this is done on the assumption that clien...

  • Page 410

    Idp traffic shaping has a special cli command associated with it called idppipes and this can examine and manipulate the hosts which are currently subject to traffic shaping. To display all hosts being traffic shaped by idp traffic shaping, the command would be: gw-world:/> idppipes -show host kbps ...

  • Page 411: 10.2.8. Logging

    If the administrator wants to guarantee a bandwidth level, say 10 megabits, for an application then an idp rule can be set up to trigger for that application with the pipe action specifying the bandwidth required. The traffic shaping pipes that are then automatically created get the highest priority...

  • Page 412: 10.3. Threshold Rules

    10.3. Threshold rules 10.3.1. Overview the objective of a threshold rule is to have a means of detecting abnormal connection activity as well as reacting to it. An example of a cause for such abnormal activity might be an internal host becoming infected with a virus that is making repeated connectio...

  • Page 413: 10.3.4. Rule Actions

    • network based - the threshold is applied to all connections matching the rules as a group. 10.3.4. Rule actions when a threshold rule is triggered one of two responses are possible: • audit - leave the connection intact but log the event. • protect - drop the triggering connection. Logging would b...

  • Page 414: 10.4.1. Overview

    10.4. Server load balancing 10.4.1. Overview the server load balancing (slb) feature in netdefendos is a powerful tool that can improve the following aspects of network applications: • performance • scalability • reliability • ease of administration the primary benefit of slb is to allow the network...

  • Page 415

    The additional benefits of slb besides from improving performance and scalability, slb provides a number of other benefits: • slb increases the reliability of network applications by actively monitoring the servers sharing the load. Slb can detect when a server fails or becomes congested and will no...

  • Page 416

    To the same host. Network stickiness this mode is similar to ip stickiness except that by using a subnet mask, a range of hosts in a subnet can be specified. 10.4.4. The distribution algorithm there are several ways to determine how a load is shared across a server farm. Netdefendos slb supports the...

  • Page 417

    When the round robin algorithm is used, the first arriving requests r1 and r2 from client 1 are both assigned to one sever, say server 1, according to stickiness. The next request r3 from client 2 is then routed to server 2. When r4 from client 3 arrives, server 1 gets back its turn again and will b...

  • Page 418: 10.4.6. Slb_Sat Rules

    10.4.5. Server health monitoring slb uses server health monitoring to continuously check the condition of the servers in an slb configuration. Slb can monitor different osi layers to check the condition of each server. Regardless of the algorithms used, if a server is deemed to have failed, slb will...

  • Page 419

    Rule name rule type src. Interface src. Network dest. Interface dest. Network web_slb_alw allow any all-nets core ip_ext note that the destination interface is specified as core, meaning netdefendos itself deals with this. The key advantage of having a separate allow rule is that the webservers can ...

  • Page 420

    1. Go to rules > ip rule sets > main > add > ip rule 2. Enter: • name: web_slb_nat • action: nat • service: http • source interface: lan • source network: lannet • destination interface: core • destination network: ip_ext 3. Click ok e. Specify an allow ip rule for the external clients: 1. Go to rul...

  • Page 421

    10.4.6. Slb_sat rules chapter 10. Traffic management 421.

  • Page 422: 11.1. Overview

    Chapter 11. High availability this chapter describes the high availability fault-tolerance feature in netdefend firewalls. • overview, page 422 • ha mechanisms, page 424 • ha setup, page 427 • ha issues, page 431 • ha advanced settings, page 432 11.1. Overview ha clusters netdefendos high availabili...

  • Page 423

    The heartbeat mechanism is discussed below in more depth in section 11.2, “ha mechanisms”. Cluster management an ha cluster of two netdefend firewalls is managed as a single unit with a unique cluster name which appears in the management interface as a single logical netdefend firewall. Administrati...

  • Page 424: 11.2. Ha Mechanisms

    11.2. Ha mechanisms this section discusses im more depth the mechanisms netdefendos uses to implement the high availability feature. Basic principles d-link ha provides a redundant, state-synchronized hardware configuration. The state of the active unit, such as the connection table and other vital ...

  • Page 425

    Failover time the time for failover is typically about one second which means that clients may experience a failover as a slight burst of packet loss. In the case of tcp, the failover time is well within the range of normal retransmit timeouts so tcp will retransmit the lost packets within a very sh...

  • Page 426

    Will lose their synchronization with each other. In other words, the inactive unit will no longer have a correct copy of the state of the active unit. A failover will not occur in this situation since the inactive unit will realize that synchronization has been lost. Failure of the sync interface re...

  • Page 427: 11.3. Ha Setup

    11.3. Ha setup this section provides a step-by-step guide for setting up an ha cluster. 11.3.1. Ha hardware setup the steps for the setup of hardware in an ha cluster are as follows: 1. Start with two physically similar netdefend firewalls. Both may be newly purchased or an existing unit may have a ...

  • Page 428

    Typical ha cluster network connections the illustration below shows the arrangement of typical ha cluster connections in a network. All interfaces on the master unit would normally also have corresponding interfaces on the slave unit and these would be connected to the same networks. This is achieve...

  • Page 429

    2. Go to system > high availability. 3. Check the enable high availability checkbox. 4. Set the cluster id. This must be unique for each cluster. 5. Choose the sync interface. 6. Select the node type to be master. 7. Go to objects > address book and create an ip4 ha address object for each interface...

  • Page 430

    Number on the right is the maximum number of connections allowed by the license. The following points are also relevant to cluster setup: • if this is not the first cluster in a network then the cluster id must be changed for the cluster so that it is unique (the default value is 0). The cluster id ...

  • Page 431: 11.4. Ha Issues

    11.4. Ha issues the following points should be kept in mind when managing and configuring an ha cluster. Snmp snmp statistics are not shared between master and slave. Snmp managers have no failover capabilities. Therefore both firewalls in a cluster need to be polled separately. Using individual ip ...

  • Page 432

    11.5. Ha advanced settings the following netdefendos advanced settings are available for high availability: sync buffer size how much sync data, in kbytes, to buffer while waiting for acknowledgments from the cluster peer. Default: 1024 sync packet max burst the maximum number of state sync packets ...

  • Page 433

    11.5. Ha advanced settings chapter 11. High availability 433.

  • Page 434: Chapter 12. Zonedefense

    Chapter 12. Zonedefense this chapter describes the d-link zonedefense feature. • overview, page 434 • zonedefense switches, page 435 • zonedefense operation, page 436 12.1. Overview zonedefense controls switches zonedefense allows a netdefend firewall to control locally attached switches. It can be ...

  • Page 435: 12.2. Zonedefense Switches

    12.2. Zonedefense switches switch information regarding every switch that is to be controlled by the firewall has to be manually specified in the firewall configuration. The information needed in order to control a switch includes: • the ip address of the management interface of the switch • the swi...

  • Page 436: 12.3.1. Snmp

    12.3. Zonedefense operation 12.3.1. Snmp simple network management protocol (snmp) is an application layer protocol for complex network management. Snmp allows the managers and managed devices in a network to communicate with each other. Snmp managers a typical managing device, such as a netdefend f...

  • Page 437

    As a complement to threshold rules, it is also possible to manually define hosts and networks that are to be statically blocked or excluded. Manually blocked hosts and networks can be blocked by default or based on a schedule. It is also possible to specify which protocols and protocol port numbers ...

  • Page 438: 12.3.5. Limitations

    2. For addresses choose the object name of the firewall's interface address 192.168.1.1 from the available list and put it into the selected list. 3. Click ok configure an http threshold of 10 connections/second: 1. Go to traffic management > threshold rules > add > threshold rule 2. For the thresho...

  • Page 439

    Of latency time to implement blocking once the rule is triggered. Some models can activate blocking in less than a second while some models may require a minute or more. A second difference is the maximum number of rules supported by different switches. Some switches support a maximum of 50 rules wh...

  • Page 440

    12.3.5. Limitations chapter 12. Zonedefense 440

  • Page 441: 13.1. Ip Level Settings

    Chapter 13. Advanced settings this chapter describes the configurable advanced settings for netdefendos. The settings are divided up into the following categories: note: activating changes after any advanced setting is changed, the new netdefendos configuration must be deployed in order for the new ...

  • Page 442

    Block 0.0.0.0 as source address. Default: drop block 0 net block 0.* as source addresses. Default: droplog block 127 net block 127.* as source addresses. Default: droplog block multicast src block multicast both source addresses (224.0.0.0 - 255.255.255.255). Default: droplog ttl min the minimum ttl...

  • Page 443

    Securemoteudp compatibility allow ip data to contain eight bytes more than the udp total length field specifies. Checkpoint securemote violates nat-t drafts. Default: disabled ip option sizes verifies the size of "ip options". These options are small blocks of information that may be added to the en...

  • Page 444

    Ip reserved flag indicates what netdefendos will do if there is data in the "reserved" fields of ip headers. In normal circumstances, these fields should read 0. Used by os fingerprinting. Default: droplog strip dontfragment strip the don’t fragment flag for packets equal to or smaller than the size...

  • Page 445: 13.2. Tcp Level Settings

    13.2. Tcp level settings tcp option sizes verifies the size of tcp options. This function acts in the same way as ipoptionsizes described above. Default: validatelogbad tcp mss min determines the minimum permissible size of the tcp mss. Packets containing maximum segment sizes below this limit are h...

  • Page 446

    Tcp auto clamping automatically clamp tcp mss according to mtu of involved interfaces, in addition to tcpmssmax. Default: enabled tcp zero unused ack determines whether netdefendos should set the ack sequence number field in tcp packets to zero if it is not used. Some operating systems reveal sequen...

  • Page 447

    Initially intended to be used in negotiating for the use of better checksums in tcp. However, these are not understood by any today's standard systems. As netdefendos cannot understand checksum algorithms other than the standard algorithm, these options can never be accepted. The altchkreq option is...

  • Page 448

    Tcp syn/fin the tcp fin flag together with syn; normally invalid (strip=strip fin). Default: droplog tcp fin/urg specifies how netdefendos will deal with tcp packets with both fin (finish, close connection) and urg flags turned on. This should normally never occur, as you do not usually attempt to c...

  • Page 449

    Tcp sequence number validation is only possible on connections tracked by the state-engine (not on packets forwarded using a fwdfast rule). Possible values are: ignore - do not validate. Means that sequence number validation is completely turned off. Validatesilent - validate and pass on. Validatelo...

  • Page 450: 13.3. Icmp Level Settings

    13.3. Icmp level settings icmp sends per sec limit specifies the maximum number of icmp messages netdefendos may generate per second. This includes ping replies, destination unreachable messages and also tcp rst packets. In other words, this setting limits how many rejects per second may be generate...

  • Page 451: 13.4. State Settings

    13.4. State settings connection replace allows new additions to the netdefendos connection list to replace the oldest connections if there is no available space. Default: replacelog log open fails in some instances where the rules section determines that a packet should be allowed through, the state...

  • Page 452

    Default: log log connection usage this generates a log message for every packet that passes through a connection that is set up in the netdefendos state-engine. Traffic whose destination is the netdefend firewall itself, for example netdefendos management traffic, is not subject to this setting. The...

  • Page 453

    13.5. Connection timeout settings the settings in this section specify how long a connection can remain idle, that is to say with no data being sent through it, before it is automatically closed. Please note that each connection has two timeout values: one for each direction. A connection is closed ...

  • Page 454

    Other idle lifetime specifies in seconds how long connections using an unknown protocol can remain idle before it is closed. Default: 130 13.5. Connection timeout settings chapter 13. Advanced settings 454.

  • Page 455

    13.6. Length limit settings this section contains information about the size limits imposed on the protocols directly under ip level, such as tcp, udp and icmp. The values specified here concern the ip data contained in packets. In the case of ethernet, a single packet can contain up to 1480 bytes o...

  • Page 456

    Specifies in bytes the maximum size of an ah packet. Ah, authentication header, is used by ipsec where only authentication is applied. This value should be set at the size of the largest packet allowed to pass through the vpn connections, regardless of its original protocol, plus approx. 50 bytes. D...

  • Page 457

    13.7. Fragmentation settings ip is able to transport up to 65536 bytes of data. However, most media, such as ethernet, cannot carry such huge packets. To compensate, the ip stack fragments the data to be sent into separate packets, each one given their own ip header and information that will help th...

  • Page 458

    Default: check8 – compare 8 random locations, a total of 32 bytes failed fragment reassembly reassemblies may fail due to one of the following causes: • some of the fragments did not arrive within the time stipulated by the reasstimeout or reasstimelimit settings. This may mean that one or more frag...

  • Page 459

    • nolog - no logging is carried out under normal circumstances. • logsuspect - logs duplicated fragments if the reassembly procedure has been affected by "suspect" fragments. • logall - always logs duplicated fragments. Default: logsuspect fragmented icmp other than icmp echo (ping), icmp messages s...

  • Page 460

    Reassembly illegal limit once a whole packet has been marked as illegal, netdefendos is able to retain this in memory for this number of seconds in order to prevent further fragments of that packet from arriving. Default: 60 13.7. Fragmentation settings chapter 13. Advanced settings 460

  • Page 461

    13.8. Local fragment reassembly settings max concurrent maximum number of concurrent local reassemblies. Default: 256 max size maximum size of a locally reassembled packet. Default: 10000 large buffers number of large ( over 2k) local reassembly buffers (of the above size). Default: 32 13.8. Local f...

  • Page 462

    13.9. Miscellaneous settings udp source port 0 how to treat udp packets with source port 0. Default: droplog port 0 how to treat tcp/udp packets with destination port 0 and tcp packets with source port 0. Default: droplog watchdog time number of non-responsive seconds before watchdog is triggered (0...

  • Page 463

    13.9. Miscellaneous settings chapter 13. Advanced settings 463.

  • Page 464: Updates

    Appendix a. Subscribing to security updates introduction the netdefendos anti-virus (av) module, the intrusion detection and prevention (idp) module and the dynamic web content filtering module all function using external d-link databases which contain details of the latest viruses, security threats...

  • Page 465

    An anti-virus update can similarly be initiated with the command: gw-world:/> updatecenter -update antivirus querying update status to get the status of idp updates use the command: gw-world:/> updatecenter -status idp to get the status of av updates: gw-world:/> updatecenter -status antivirus query...

  • Page 466

    Appendix b. Idp signature groups for idp scanning, the following signature groups are available for selection. These groups are available only for the d-link advanced idp service. There is a version of each group under the three types of ids, ips and policy. For further information see section 6.5, ...

  • Page 467

    Group name intrusion type ftp_formatstring format string attack ftp_general ftp protocol and implementation ftp_login login attacks ftp_overflow ftp buffer overflow game_bomberclone bomberclone game game_general generic game servers/clients game_unreal unreal game server http_apache apache httpd htt...

  • Page 468

    Group name intrusion type pop3_dos denial of service for pop pop3_general post office protocol v3 pop3_login-attacks password guessing and related login attack pop3_overflow pop3 server overflow pop3_request-errors request error portmapper_general portmapper print_general lp printing server: lpr lpd...

  • Page 469

    Group name intrusion type tftp_operation operation attack tftp_overflow tftp buffer overflow attack tftp_reply tftp reply attack tftp_request tftp request attack trojan_general trojan udp_general general udp udp_popup pop-up window for ms windows upnp_general upnp version_cvs cvs version_svn subvers...

  • Page 470

    Appendix c. Verified mime filetypes some netdefendos application layer gateways (algs) have the optional ability to verify that the contents of a downloaded file matches the type that the filetype in the filename indicates. The filetypes for which mime verification can be done are listed in this app...

  • Page 471

    Filetype extension application cpl windows control panel extension file dbm database file dcx graphics multipage pcx bitmap file deb debian linux package file djvu djvu file dll windows dynamic link library file dpa dpa archive data dvi tex device independent document eet eet archive egg allegro dat...

  • Page 472

    Filetype extension application mpv mpeg-1 video file microsoft files microsoft office files, and other microsoft files msa atari msa archive data niff, nif navy interchange file format bitmap noa nancy video codec nsf nes sound file obj, o windows object file, linux object file ocx object linking an...

  • Page 473

    Filetype extension application tfm tex font metric data tiff, tif tagged image format file tnef transport neutral encapsulation format torrent bittorrent metainfo file ttf truetype font txw yamaha tx wave audio files ufa ufa archive data vcf vcard file viv vivoactive player streaming video file wav ...

  • Page 474

    Appendix d. The osi framework overview the open systems interconnection model defines a framework for inter-computer communications. It categorizes different protocols for a great variety of network applications into seven smaller, more manageable layers. The model describes how data from an applica...

  • Page 475

    Appendix e. D-link worldwide offices below is a complete list of d-link worldwide sales offices. Please check your own country area's local website for further details regarding support of d-link products as well as contact details for local support. Australia 1 giffnock avenue, north ryde, nsw 2113...

  • Page 476

    Italy via nino bonnet n. 6/b, 20154 – milano, italy. Tel: 39-02-2900-0676, fax: 39-02-2900-1723. Website: www.Dlink.It latinamerica isidora goyeechea 2934, ofcina 702, las condes, santiago – chile. Tel: 56-2-232-3185, fax: 56-2-232-0923. Website: www.Dlink.Cl luxemburg rue des colonies 11, b-1000 br...

  • Page 477: Alphabetical Index

    Alphabetical index a access rules, 201 accounting, 56 interim messages, 58 limitations with nat, 59 messages, 56 system shutdowns, 59 address book, 73 ethernet addresses in, 75 folders, 77 ip addresses in, 73 address groups, 76 address translation, 292 admin account, 26 changing password for, 35 mul...

  • Page 478

    Block multicast src setting, 442 boot menu (see console boot menu) bootp, 195 bpdu relaying, 184 broadcast enet sender setting, 186 c cam size setting, 185 cam to l3 cache dest learning setting, 184 ca servers access, 383 client access, 384 fqdn resolution, 385 certificates, 114 ca authority, 114 ce...

  • Page 479

    Dynamic l3c size setting, 185 dynamic max connections setting, 452 dynamic routing policy, 159 dyndns service, 125 e enable sensors setting, 61 end of life procedures, 71 esmtp extensions, 217 ethernet interface, 85 changing ip addresses, 86 cli command summary, 88 default gateway, 87 ip address, 86...

  • Page 480

    Illegal fragments setting, 457 initial silence (ha) setting, 432 insertion attack prevention, 277 interface alias (snmp) setting, 65 interface description (snmp) setting, 65 interfaces, 84 disabling, 85 groups, 98 loopback, 84, 85 physical, 84 internet key exchange (see ike) interval between synchro...

  • Page 481

    Max tcp length setting, 455 max time drift setting, 123 max transactions (dhcp) setting, 196 max udp length setting, 455 memlog, 52 mime filetype verification in ftp alg, 209 in http alg, 206 in pop3 alg, 224 in smtp alg, 215 list of filetypes, 470 min broadcast ttl setting, 444 minimum fragment len...

  • Page 482

    Static, 129 the all-nets route, 135 s sa (see security association) safestream, 270 sat, 300 ip rules, 109 multiplex rule, 162 port forwarding, 300 second rule destination, 300 schedules, 112 scp, 41 scripting (see cli scripts) secondary time server setting, 123 secure copy (see scp) securemoteudp c...

  • Page 483

    In zonedefense, 436 time synchronization, 119 time sync server type setting, 123 time zone setting, 122 tls alg, 248 traffic shaping, 390 bandwidth guarantees, 398 bandwidth limiting, 393 fwdfast ip rule exclusion, 392 groups, 399 objectives, 390 precedences, 396 recommendations, 400 summary, 402 wi...