Enabling Stp - Cisco 6500 Series Software Configuration Manual

Chapter 15 Configuring STP and IEEE 802.1s MST

Enabling STP

STP is enabled by default on VLAN 1 and on all newly created VLANs.
Note
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:
Command
Step 1
Router(config)# spanning-tree vlan vlan_ID
Router(config)# default spanning-tree vlan
vlan_ID
Router(config)# no spanning-tree vlan vlan_ID
Step 2
Router(config)# end
Step 3
Router# show spanning-tree vlan vlan_ID
Do not disable spanning tree on a VLAN unless all switches and bridges in the VLAN have spanning
Caution
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.
We do not recommend disabling spanning tree, even in a topology that is free of physical loops. Spanning
Caution
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#
Because STP is enabled by default, entering a show running command to view the resulting
Note
configuration does not display the command you entered to enable STP.
78-14099-04
Purpose
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
Reverts all STP parameters to default values for the
specified VLAN.
Disables STP on the specified VLAN; see the following
Cautions for information regarding this command.
Exits configuration mode.
Verifies that STP is enabled.
Catalyst 6500 Series Switch Cisco IOS Software Configuration Guide—Release 12.1 E
Configuring STP
15-21).
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