Configuring Stp Port Priority - Cisco 7604 Configuration Manual

Chapter 20 Configuring STP and Prestandard IEEE 802.1s MST

Configuring STP Port Priority

If a loop occurs, STP considers port priority when selecting a LAN port to put into the forwarding state.
You can assign higher priority values to LAN ports that you want STP to select first and lower priority
values to LAN ports that you want STP to select last. If all LAN ports have the same priority value, STP
puts the LAN port with the lowest LAN port number in the forwarding state and blocks other LAN ports.
The possible priority range is 0 through 240 (default 128), configurable in increments of 16.
When the LAN port is configured as a trunk port, you can specify a different port priority for each VLAN
carried by the trunk. VLANs not configured with a VLAN port priority default to using the spanning-tree
port priority. Do not configure VLAN port priority for access ports.
To configure the STP port priority of a Layer 2 LAN interface, perform this task:
Command
Step 1
Router(config)# interface {{ type
{port-channel port_channel_number }}
Step 2
Router(config-if)# spanning-tree port-priority
port_priority
Router(config-if)# no spanning-tree port-priority
Step 3
Router(config-if)# spanning-tree vlan vlan_ID
port-priority port_priority
Router(config-if)# [no] spanning-tree vlan
vlan_ID port-priority
Step 4
Router(config-if)# end
Step 5
Router# show spanning-tree interface { type
slot/port } | {port-channel port_channel_number }
Router# show spanning-tree vlan vlan_ID
1. type = ethernet, fastethernet, gigabitethernet, or tengigabitethernet
This example shows how to configure the STP port priority of Fast Ethernet port 4/4:
Router# configure terminal
Router(config)# interface fastethernet 4/4
Router(config-if)# spanning-tree port-priority 160
Router(config-if)# end
Router#
This example shows how to verify the configuration of Fast Ethernet port 4/4:
Router# show spanning-tree interface fastethernet 4/4
Vlan
---------------- ---- --- --------- -------- --------------------------------
VLAN0001
VLAN0006
...
VLAN0198
VLAN0199
VLAN0200
Router#
OL-4266-08
Purpose
1
Selects an interface to configure.
slot/port } |
Configures the port priority for the LAN interface. The
port_priority value can be from 0 to 240 in increments
of 16.
Reverts to the default port priority value.
Configures the VLAN port priority for the LAN interface.
The port_priority value can be from 0 to 240 in
increments of 16. The vlan_ID value can be 1 through
4094, except reserved VLANs (see
page
Reverts to the default VLAN port priority value.
Exits configuration mode.
1
Verifies the configuration.
Role Sts Cost Prio.Nbr Status
Back BLK 200000 160.196
Back BLK 200000 160.196
Back BLK 200000 160.196
Back BLK 200000 160.196
Back BLK 200000 160.196
Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
14-2).
P2p
P2p
P2p
P2p
P2p
Configuring STP
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