Cisco Catalyst 3750-X User Manual

20-17
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-21521-01
Chapter 20 Configuring STP
Configuring Spanning-Tree Features
Beginning in privileged EXEC mode, follow these steps to configure a switch to become the root for the
specified VLAN. This procedure is optional.
To return to the default setting, use the no spanning-tr
ee vlan vlan-id root global configuration
command.
Configuring a Secondary Root Switch
When you configure a switch as the secondary root, the switch priority is modified from the default value
(32768) to 28672. The switch is then likely to become the root switch for the specified VLAN if the
primary root switch fails. This is assuming that the other network switches use the default switch priority
of 32768 and therefore are unlikely to be
come the root switch.
You can execute this command on more t
han one switch to configure multiple backup root switches. Use
the same network diameter and hello-time values that you used when you configured the primary root
switch with the spanning-tree vlan vlan-id root primary global configuration command.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
spanning-tree vlan vlan-id root primary
[diameter net-diameter [hello-time seconds]]
Configure a switch to become the 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; the default is 2.
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.

Cisco Catalyst 3750-X Specifications

General

Brand	Cisco
Model	Catalyst 3750-X
Category	Switch
Language	English