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Catalyst 2950 Desktop Switch Software Configuration Guide
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Chapter 12 Configuring RSTP and MSTP Configuring RSTP and MSTP Features
Note Th e ro ot swi tch fo r eac h s pan ning -t ree inst anc e shoul d b e a ba ckbon e or dist ribution sw itch . D o no t
configure an access switch as the spanning-tree primary root.
Use the diameter keyword, whic h is available onl y for MST instance 0, to spec ify the Layer 2 network
diamet er (that is, the maximu m numbe r of switch hop s between a ny two end stations in the Layer 2
network). When you specify the network diameter, the switch automatically sets an optimal hello time,
forward- delay time , and max imum-a ge time for a network of tha t diameter, which can signi ficantly
reduce the convergence time. You can use the hello keyword to override the automatically calculated
hello time.
Note We reco mm end tha t y ou avoid manua lly configu ring the h ello tim e, forwa rd -del ay t im e, and
maximum-a ge tim e by using the spanning-tree mst hello-time, spanning-tree mst f o rw ard-time, and
the spanning-tr ee mst max-age global conf iguratio n commands after conf iguring the switch as th e root
switch.
Beginning in privileged EXEC mode, follow these steps to configure a switch as the root switch:
To return the switch to its default setting, use the no spanning-tree mst instance-id root globa l
configurati on comm a nd.
Command Purpose
Step 1 configure terminal Enter glob al configura tion mod e.
Step 2 spanning-tree mst instance-id root primar y
[diameter net-diameter [hello-time seconds]] Configure a switch as the root switch.
•For instance-id, the range is 0 to 15.
•(Optiona l) For diameter net-diameter, specify the
maximu m num be r of sw itche s b etwe en a ny two end
stations. The range is 2 to 7. This keyword is available
only for MST inst anc e 0.
•(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 se conds ; t he
default is 2 se cond s.
Step 3 end Return to p rivileged EXEC mode.
Step 4 show spanning-tree mst instance-id Verify your e ntri es.
Step 5 copy running-config startup-config (Optiona l) Save your entries in the co nfigurati on file.