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Catalyst 2950 Desktop Switch Software Configuration Guide
78-14982-01
Chapter 11 Configuring STP
Configuring Spanning-Tree Features
Beginning in privileged EXEC mode, follow these steps to a switch to become the root for the specified
VLAN:
To return the switch to its default setting, use the no spanning-tree vlan vlan-id root global
configuration command.
Configuring a Secondary Root Switch
When you configure a Catalyst 2950 switch that supports the extended system ID 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 become
the root switch. For Catalyst 2950 switches without the extended system ID support (software earlier
than Release 12.1(9)EA1), the switch priority is changed to 16384.
You can execute this command on more than one switch to configure multiple backup root switches. Use
the same network diameter and hello-time values as 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, the range is 1 to 4094 when the EI is installed
and 1 to 1005 when the SI is installed. Do not enter leading
zeros.
• (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.
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.