Configuring The Root Switch; Configuring The Port Priority - Cisco ONS 15454 SDH Configuration Manual

Chapter 7 Configuring STP and RSTP
Beginning in privileged EXEC mode, follow these steps to disable STP or RSTP on a per-VLAN basis:
Command
Step 1
Router# configure terminal
Step 2
Router(config)# interface interface-id
Step 3
Router(config-if)# bridge-group
bridge-group-number spanning disabled
Step 4
Router(config-if)# end
To reenable STP, use the no bridge-group bridge-group-number spanning disabled interface-level
configuration command.

Configuring the Root Switch

The switch maintains a separate spanning-tree instance for each active VLAN configured on it. A
bridge ID, consisting of the switch priority and the switch MAC address, is associated with each
instance. For each VLAN, the switch with the lowest bridge ID becomes the root switch for that VLAN.
If your network consists of switches that both do and do not support the extended system ID, it is unlikely
Note
that the switch with the extended system ID support will become the root switch. The extended system
ID increases the switch priority value every time the bridge ID is greater than the priority of the
connected switches that are running older software.

Configuring the Port Priority

If a loop occurs, spanning tree uses the port priority when selecting an interface to put into the
forwarding state. You can assign higher priority values (lower numerical values) to interfaces that you
want selected first, and lower priority values (higher numerical values) that you want selected last. If all
interfaces have the same priority value, spanning tree puts the interface with the lowest interface number
in the forwarding state and blocks the other interfaces.
Beginning in privileged EXEC mode, follow these steps to configure the port priority of an interface:
Command
Step 1
Router# configure terminal
Step 2
Router(config)# interface
interface-id
Cisco ONS 15454 and Cisco ONS 15454 SDH Ethernet Card Software Feature and Configuration Guide, R8.0
Purpose
Enters the global configuration mode.
Enters the interface configuration mode.
Disables STP or RSTP on a per-interface basis.
Returns to privileged EXEC mode.
Purpose
Enters the global configuration mode.
Enters the interface configuration mode, and specifies an
interface to configure.
Valid interfaces include physical interfaces and
port-channel logical interfaces (port-channel
port-channel-number).
Configuring the Root Switch
7-17