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Catalyst 6500 Series Switch Cisco IOS Software Configuration Guide—Release 12.1 E
78-14099-04
Chapter 15 Configuring STP and IEEE 802.1s MST
Configuring STP
Enabling STP
Note STP is enabled by default on VLAN 1 and on all newly created VLANs.
You can enable STP on a per-VLAN basis. The Catalyst 6500 series switch maintains a separate instance
of STP for each VLAN (except on VLANs on which you disable STP).
To enable STP on a per-VLAN basis, perform this task:
Caution Do not disable spanning tree on a VLAN unless all switches and bridges in the VLAN have spanning
tree disabled. You cannot disable spanning tree on some switches and bridges in a VLAN and leave it
enabled on other switches and bridges in the VLAN. This action can have unexpected results because
switches and bridges with spanning tree enabled will have incomplete information regarding the physical
topology of the network.
Caution We do not recommend disabling spanning tree, even in a topology that is free of physical loops. Spanning
tree serves as a safeguard against misconfigurations and cabling errors. Do not disable spanning tree in
a VLAN without ensuring that there are no physical loops present in the VLAN.
This example shows how to enable STP on VLAN 200:
Router# configure terminal
Router(config)# spanning-tree vlan 200
Router(config)# end
Router#
Note Because STP is enabled by default, entering a show running command to view the resulting
configuration does not display the command you entered to enable STP.
Command Purpose
Step 1 Router(config)# spanning-tree vlan vlan_ID Enables STP on a per-VLAN basis. The vlan_ID value
can be 1 through 4094, except reserved VLANs (see
Table 15-5 on page 15-21).
Router(config)# default spanning-tree vlan
vlan_ID
Reverts all STP parameters to default values for the
specified VLAN.
Router(config)# no spanning-tree vlan vlan_ID Disables STP on the specified VLAN; see the following
Cautions for information regarding this command.
Step 2 Router(config)# end Exits configuration mode.
Step 3 Router# show spanning-tree vlan vlan_ID Verifies that STP is enabled.