D-Link DES-3226 User Manual - Spanning Tree Protocol

DES-3226 NWay Standalone Fast Ethernet Switch User’s Guide 

•  MAC address filtering – the manual entry of specific MAC addresses to be filtered from the 

network. Packets sent from one manually entered MAC address can be filtered from the 

network. The entry may be specified as source, destination, or both. 

Spanning Tree Protocol 

The IEEE 802.1D Spanning Tree Protocol allows for the blocking of links between switches that form 

loops within the network. When multiple links between switches are detected, a primary link is 

established. Duplicated links are blocked from use and become standby links. The protocol allows for 

the duplicate links to be used in the event of a failure of the primary link. Once the Spanning Tree 

Protocol is configured and enabled, primary links are established and duplicated links are blocked 

automatically. The reactivation of the blocked links (at the time of a primary link failure) is also 

accomplished automatically – without operator intervention. 

This automatic network reconfiguration provides maximum uptime to network users. However, the 

concepts of the Spanning Tree Algorithm and protocol are a complicated and complex subject and must 

be fully researched and understood. It is possible to cause serious degradation of the performance of 

the network if the Spanning Tree is incorrectly configured. Please read the following before making any 

changes from the default values. 

The DES-3226 STP allows two levels of spanning trees to be configured. The first level constructs a 

spanning tree on the links between switches. This is referred to as the Switch  or  Global  level. The 

second level is on a port basis. Ports are configured as individual members of a spanning tree and the 

algorithm and protocol are applied to the specified ports. This is referred to as the Port or VLAN level. 

The Switch STP performs the following functions: 

•  Creates a single spanning tree from any combination of switching or bridging elements. 

•  Automatically reconfigures the spanning tree to compensate for the failure, addition, or removal 

of any element in the tree. 

•  Reconfigures the spanning tree without operator intervention. 

STP Operation Levels 

The Switch allows for two levels of operation: the switch level and the port level. The switch level forms 

a spanning tree consisting of links between one or more switches. The port level constructs a spanning 

tree consisting of groups of one or more ports. The STP operates in much the same way for both levels. 

On the switch level, STP calculates the Bridge Identifier for each switch and then sets the Root Bridge 

and the Designated Bridges. 

On the port level, STP sets the Root Port and the Designated Ports. 

The following are the user-configurable STP parameters for the switch level: 

Parameter Description 

Default 

Value 

Bridge Identifier 

(Not user-

configurable except 

by setting  priority 

A combination of the User-set 

priority and the switch’s MAC 

address.  The Bridge Identifier 

consists of two parts: a 16-bit 

priority and a 48-bit Ethernet MAC 

32768 + MAC 

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