Configuring Spanning Tree Parameters Configuring STP Port Parameters
OmniSwitch AOS Release 6 Network Configuration Guide September 2009 page 13-37
Restricting Port Roles (Root Guard)
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 bridge cist slot/port restricted-role command or the bridge
1x1 slot/port restricted-role 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.
Restricting TCN Propagation
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 bridge cist slot/port restricted-tcn command. Similarly a port in 1x1 instance can be restricted by
using the bridge 1x1 slot/port restricted-tcn 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
Limiting BPDU Transmission
The number of BPDUs to be transmitted per port per second can be limited using the bridge cist txhold-
count command for a CIST instance or bridge 1x1 txholdcount 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
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