Enabling Stp - Cisco Catalyst 4500 Series Software Configuration Manual

Configuring STP
The spanning tree commands described in this chapter can be configured on any interface except those
Note
configured with the no switchport command.

Enabling STP

Note By default, spanning tree is enabled on all the VLANs.
You can enable a spanning tree on a per-VLAN basis. The switch maintains a separate instance of
spanning tree for each VLAN (except on VLANs on which you have disabled a spanning tree).
To enable a spanning tree on a per-VLAN basis, perform this task:
Command
Step 1
Switch# configure terminal
Step 2
Switch(config)# spanning-tree vlan vlan_ID
Step 3
Switch(config)# end
Step 4
Switch# show spanning-tree vlan vlan_ID
This example shows how to enable a spanning tree on VLAN 200:
Switch# configure terminal
Switch(config)# spanning-tree vlan 200
Switch(config)# end
Switch#
Because spanning tree is enabled by default, entering a show running command to view the resulting
Note
configuration does not display the command you entered to enable spanning tree.
This example shows how to verify that spanning tree is enabled on VLAN 200:
Switch# show spanning-tree vlan 200
VLAN200 is executing the ieee compatible Spanning Tree protocol
Bridge Identifier has priority 32768, address 0050.3e8d.6401
Configured hello time 2, max age 20, forward delay 15
Current root has priority 16384, address 0060.704c.7000
Root port is 264 (FastEthernet5/8), cost of root path is 38
Topology change flag not set, detected flag not set
Number of topology changes 0 last change occurred 01:53:48 ago
Times:
Timers: hello 0, topology change 0, notification 0
Port 264 (FastEthernet5/8) of VLAN200 is forwarding
Port path cost 19, Port priority 128, Port Identifier 129.9.
Designated root has priority 16384, address 0060.704c.7000
Designated bridge has priority 32768, address 00e0.4fac.b000
Designated port id is 128.2, designated path cost 19
Timers: message age 3, forward delay 0, hold 0
Number of transitions to forwarding state: 1
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
23-8
hold 1, topology change 24, notification 2
hello 2, max age 14, forward delay 10
Purpose
Enters global configuration mode.
Enables spanning tree for VLAN vlan_id. The vlan_ID value
can range from 1 to 4094.
Exits configuration mode.
Verifies that spanning tree is enabled.
Chapter 23 Configuring STP and MST