D-Link DES-3350SR User Manual - page 116
D-Link DES-3350SR Standalone Layer 3 Switch
106
All routers connected to a common network must agree on certain parameters such as the Network Mask, the Hello Interval, and
the Router Dead Interval. These parameters are included in the hello packets, so that differences can inhibit the forming of
neighbor relationships. A detailed explanation of the receive process for Hello packets is necessary so that differences can inhibit
the forming of neighbor relationships.
The format of the Hello packet is shown below:
Hello Packet
1
Packet Length
Router ID
Area ID
Version No.
Checksum
Authentication Type
Authentication
Authentication
Network Mask
Hello Interval
Options
Router Priority
Router Dead Interval
Designated Router
Backup Designated Router
Neighbor
Figure 9 - 17. Hello Packet
Field
Description
Network Mask
The network mask associated with this interface.
Options
The optional capabilities supported by the router.
Hello Interval
The number of seconds between this router’s Hello packets.
Router Priority
This router’s Router Priority. The Router Priority is used in the
election of the DR and BDR. If this field is set to 0, the router is
ineligible become the DR or the BDR.
Router Dead Interval
The number of seconds that must pass before declaring a
silent router as down.
Designated Router
The identity of the DR for this network, in the view of the
advertising router. The DR is identified here by its IP interface
address on the network.
Backup Designated Router The identity of the Backup Designated Router (BDR) for this
network. The BDR is identified here by its IP interface address
on the network. This field is set to 0.0.0.0 if there is no BDR.
Field
Description
Neighbor
The Router IDs of each router from whom valid Hello packets
have been seen within the Router Dead Interval on the
network.
Database Description Packet
Database Description packets are OSPF packet type 2. These packets are exchanged when an adjacency is being initialized. They
describe the contents of the topological database. Multiple packets may be used to describe the database. For this purpose, a poll-
response procedure is used. One of the routers is designated to be master, the other a slave. The master seconds Database
Description packets (polls) that are acknowledged by Database Description packets sent by the slave (responses). The responses
are linked to the polls via the packets’ DD sequence numbers.