3com 4500 26-PORT User Manual

Use the 

 command to configure the current Switch as a 

secondary root of a specified spanning tree. 

Use the 

command to cancel the designation of the current Switch 

for a secondary root of a specified spanning tree.

By default, a Switch is not a secondary root.

You can designate one or more secondary roots for a spanning tree. When the 
primary root fails or is powered off, a secondary root can take its place. If more 
than one secondary root exists, the one with the smallest MAC address will 
become the primary root of the specified spanning tree.

You can configure no more than one primary root for a spanning tree but you can 
configure one or more secondary roots for it. You cannot change the bridge 
priority of a Switch if you configure it as a secondary root of a spanning tree.

To designate the Switch as a secondary root of the STP, enter the following:

<4500>system-view

System View: return to User View with Ctrl+Z.

[4500]stp root secondary

Ethernet Port View

None

Use the 

 command to enable Root protection function on a 

Switch. 

Use the 

 command to restore the default status of 

Root protection function.

By default, root protection is not enabled.

Following incorrect configuration or malicious attack, a legal root of the network 
may receive a BPDU with higher priority and lose its status as root, which causes 
problems with the network topology. Such problems may pull the higher-speed 
traffic to lower-speed links and cause network congestion.

To avoid this problem, RSTP provides Root protection function. After being 
configured with Root protection, a port always stays as a designated port. Once 
this port receives a BPDU with higher priority, it turns to listening status and will