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Catalyst 2950 Desktop Switch Software Configuration Guide
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Chapter 11 Configuring STP
Configur ing Spanning-Tree F eatures
Be gin n in g i n p r ivileged E XEC m ode, fo llow these step s to a sw i t ch to become the ro o t f or th e s p eci fied
VLAN:
To return the switch to its default setting, use the no spanning-tree vlan vlan-id root global
configurati on comm a nd.

Configur ing a Se co ndar y R oot S witch

When you configure a Catalyst 2950 switch that supports the extended system ID as the secondary root,
the swi tch pr iorit y is m odified fr om t he d efa ult value (3276 8) to 2867 2. Th e sw itch is th en li kely 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 swit ch. For Catalyst 295 0 switc hes without the extended system ID supp ort (softwar e earlier
than Release 12.1(9)EA1), the switch priority is changed to 16384.
You can e xecu te this comman d on more th an one switch to conf igure multip le backup r oot switches. U se
the same n etwork di ame ter and he llo -time values a s you used w hen y ou co nfigured the p rima ry r oot
switch with the spanning-tree vlan vlan- id root pri mar y global configuration command.
Command Purpose
Step 1 configure terminal Enter globa l configurati on mode.
Step 2 spanning-tree vlan vlan -id root primar y
[diameter net-diameter [hello-time seconds]] Configure a switch to become the root for the specif ied VLAN.
For vlan-id, th e range is 1 to 4094 when the EI is installe d
and 1 to 1005 when the SI is installed. Do not enter lea ding
zeros.
(Optiona l) For diameter net-diameter, specif y the
maximum number of switches between any two end
stations. The r ange i s 2 to 7.
(Optiona l) For hello-time seconds, specify the interval in
seconds between the generation of configuration messages
by the roo t sw itch. T he r an ge i s 1 to 10 sec onds ; t he
default is 2 se cond s.
Step 3 end Return to privileged EXEC mode.
Step 4 show spanning-tree detail Verify yo ur ent rie s.
Step 5 copy running-config startup-config (Optiona l) Save your entries in the co nfigurati on file.