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Software Configuration Guide—Release 12.2(25)SG
OL-7659-03
Chapter 13 Understanding and Configuring STP
Configuring STP
This example shows how to change the spanning tree port cost of a Fast Ethernet interface:
Switch# configure terminal
Switch(config)# interface fastethernet 5/8
Switch(config-if)# spanning-tree cost 18
Switch(config-if)# end
Switch#
This example shows how to verify the configuration of the interface when it is configured as an access
port:
Switch# show spanning-tree interface fastethernet 5/8
Port 264 (FastEthernet5/8) of VLAN200 is forwarding
Port path cost 18, Port priority 100, Port Identifier 129.8.
Designated root has priority 32768, address 0010.0d40.34c7
Designated bridge has priority 32768, address 0010.0d40.34c7
Designated port id is 128.1, designated path cost 0
Timers: message age 2, forward delay 0, hold 0
Number of transitions to forwarding state: 1
BPDU: sent 0, received 13513
Switch#
This example shows how to configure the spanning tree VLAN port cost of a Fast Ethernet interface:
Switch# configure terminal
Switch(config)# interface fastethernet 5/8
Switch(config-if)# spanning-tree vlan 200 cost 17
Switch(config-if)# end
Switch#
This example shows how to verify the configuration of VLAN 200 on the interface when it is configured
as a trunk port:
Switch# show spanning-tree vlan 200
<...output truncated...>
Port 264 (FastEthernet5/8) of VLAN200 is forwarding
Port path cost 17, Port priority 64, Port Identifier 129.8.
Designated root has priority 32768, address 0010.0d40.34c7
Designated bridge has priority 32768, address 0010.0d40.34c7
Designated port id is 128.1, designated path cost 0
Timers: message age 2, forward delay 0, hold 0
Number of transitions to forwarding state: 1
BPDU: sent 0, received 13513
<...output truncated...>
Switch#
Note The show spanning-tree command displays only information for ports with an active link (green light
is on). If there is no port with an active link, you can issue a show running-config command to confirm
the configuration.
Configuring the Bridge Priority of a VLAN
Note Exercise care when configuring the bridge priority of a VLAN. In most cases, we recommend that you
enter the spanning-tree vlan vlan_ID root primary and the spanning-tree vlan vlan_ID root
secondary commands to modify the bridge priority.