Alcatel-Lucent 6850-48 Guida Di Rete

Configuring Spanning Tree Parameters

Configuring STP Port Parameters

OmniSwitch AOS Release 6 Network Configuration Guide

page 13-37

By default, all ports are eligible for root port selection. A port in a CIST/MSTI instance or 1x1 instance 
can be prevented from becoming the root port by restricting the role of the port (also referred to as 
enabling root guard). This is done using the 

 command or the 

 command. For example:

-> bridge cist 1/24 restricted-role enable

-> bridge 1x1 100 8/1 restricted-role enable

Note that the above commands also provide optional syntax; restricted-role or root-guard. For example, 
the following two commands perform the same function:

-> bridge 1x1 2/1 restricted-role enable

-> bridge 1x1 2/1 root-guard enable

When root guard is enabled for a port, it cannot become the root port, even if it is the most likely candi-
date for becoming the root port. It will be selected as the alternate port when the root port is selected.

By default, all the ports propagate Topology Change Notifications (TCN) or Topology Changes (TC) to 
other ports. 

A port in CIST instance can be restricted from propagating Topology Change Notification (TCN) using 
the 

 command. Similarly a port in 1x1 instance can be restricted by 

using the 

 command.

For example, to restrict the port 2/2 from propagating the received TCNs and TCs to the other ports, enter 
the following command:

-> bridge cist 2/2 restricted-tcn enable

The number of BPDUs to be transmitted per port per second can be limited using the 

 command for a CIST instance or 

 commands for a 1x1 instance.

For example, to limit the number of BPDUs to be transmitted by a port in CIST instance to 5, enter the 
following command:  

-> bridge cist txholdcount 5