Configuring Stp Port Cost - Cisco 7604 Configuration Manual

Configuring STP
Fastethernet 4/4 is a trunk. Several VLANs are configured and active as shown in the example. The port
priority configuration applies to all VLANs on this interface.
The show spanning-tree interface command only displays information if the port is connected and
Note
operating. If this condition is not met, enter a show running-config interface command to verify the
configuration.
This example shows how to configure the VLAN port priority of Fast Ethernet port 4/4:
Router# configure terminal
Enter configuration commands, one per line.
Router(config)# interface fastEthernet 4/4
Router(config-if)# spanning-tree vlan 200 port-priority 64
Router(config-if)# ^Z
Router#
The configuration entered in the example only applies to VLAN 200. All VLANs other than 200 still
have a port priority of 160.
This example shows how to verify the configuration:
Router# show spanning-tree interface fastethernet 4/4
Vlan
---------------- ---- --- --------- -------- --------------------------------
VLAN0001
VLAN0006
...
VLAN0199
VLAN0200
Router#
You also can display spanning tree information for VLAN 200 using the following command:
Router# show spanning-tree vlan 200 interface fastEthernet 4/4
Interface
---------------- ---- --- --------- -------- --------------------------------
Fa4/4

Configuring STP Port Cost

The STP port path cost default value is determined from the media speed of a LAN interface. If a loop
occurs, STP considers port cost when selecting a LAN interface to put into the forwarding state. You can
assign lower cost values to LAN interfaces that you want STP to select first and higher cost values to
LAN interfaces that you want STP to select last. If all LAN interfaces have the same cost value, STP
puts the LAN interface with the lowest LAN interface number in the forwarding state and blocks other
LAN interfaces. The possible cost range is 0 through 200000000 (the default is media specific).
STP uses the port cost value when the LAN interface is configured as an access port and uses VLAN
port cost values when the LAN interface is configured as a trunk port.
Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
20-28
Role Sts Cost Prio.Nbr Status
Back BLK 200000 160.196
Back BLK 200000 160.196
Back BLK 200000 160.196
Desg FWD 200000 64.196
Role Sts Cost Prio.Nbr Status
Desg LRN 200000 64.196
Chapter 20 Configuring STP and Prestandard IEEE 802.1s MST
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