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Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
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Chapter 13 Configuring STP
Configuring Spanning-Tree Features
Beginning in privileged EXEC mode, follow these steps to configure a switch to become the secondary
root for the specified VLAN. This procedure is optional.
To return the switch to its default setting, use the no spanning-tree vlan vlan-id root global
configuration command.
Configuring the Port Priority
If a loop occurs, spanning tree uses the port priority when selecting an interface to put into the
forwarding state. You can assign higher priority values (lower numerical values) to interfaces that you
want selected first and lower priority values (higher numerical values) that you want selected last. If all
interfaces have the same priority value, spanning tree puts the interface with the lowest interface number
in the forwarding state and blocks the other interfaces.
Beginning in privileged EXEC mode, follow these steps to configure the port priority of an interface.
This procedure is optional.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
spanning-tree vlan vlan-id root secondary
[diameter net-diameter [hello-time
seconds]]
Configure a switch to become the secondary root for the specified
VLAN.
• For vlan-id, you can specify a single VLAN identified by VLAN
ID number, a range of VLANs separated by a hyphen, or a series
of VLANs separated by a comma. The range is 1 to 4094.
• (Optional) For diameter net-diameter, specify the maximum
number of switches between any two end stations. The range is
2 to 7.
• (Optional) For hello-time seconds, specify the interval in
seconds between the generation of configuration messages by
the root switch. The range is 1 to 10 seconds; the default is 2
seconds.
Use the same network diameter and hello-time values that you used
when configuring the primary root switch. See the “Configuring the
Root Switch” section on page 13-14.
Step 3
end Return to privileged EXEC mode.
Step 4
show spanning-tree detail Verify your entries.
Step 5
copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
interface interface-id Specify an interface to configure, and enter interface
configuration mode.
Valid interfaces include physical interfaces and
port-channel logical interfaces (port-channel
port-channel-number).
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