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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

Specifying the MST Region Configuration and Enabling MSTP

For two or more switches to be in the same MST region, they must have the same VLAN-to-instance
mappin g, the same con figuration revision numbe r, and the same name.
A region can h ave one me mber or m ult iple me mb ers w it h the sam e M ST co nfigurat ion; ea c h m embe r
must be ca pabl e of pr oces sin g RSTP BPD Us . The re is no li mit t o the n umb er of MS T regi on s in a
network, but each region can support up t o 16 spanning-tree instances. You can a ssi gn a VLA N to onl y
one spanning-tree instance at a time.
Beginning in privileged EXEC mode, follow these steps to specify the MST region configuration and
enab le MSTP. This proc edure is re quired .
To return to the default M ST region c onfiguration, use the no spanning- tree mst configuration global
configuration command. To return to the default VLAN-to-instance map, use the no instance instance-id
[vlan vlan-range] MST co nfigurat ion c omm and. To re turn t o the defau lt na me, use the no name MST
Command Purpose
Step 1 configure terminal Enter g lo bal c onfigurat ion m ode.
Step 2 spanning-tree mst configuration Enter M ST c onfigurati on m ode.
Step 3 instance instance-id vlan vlan-range Map VLANs to an MST instance.
•For instance-id, th e range is 1 to 15.
•For vlan vlan-range, the range is 1 to 4094.
When you map VLANs to a n MST instan ce , th e m apping is incre ment al,
and the range of VLANs specified is added or removed to the existing
ones.
To specify a range, use a hyphen; for example, instance 1 vlan 1-63 maps
VLANs 1 throug h 63 to MST insta nce 1.
To spec ify a ser ies, us e a comma; for e xampl e, instance 1 vlan 10, 20, 30
maps VLAN s 10, 20, an d 30 to MST inst ance 1.
Step 4 name name Specify t he configura ti on n ame. Th e name string ha s a m axim um leng th
of 32 characters and is case sensitive.
Step 5 revision version Specify th e configurat ion r evision n umber. The rang e is 0 to 655 35.
Step 6 show pending Verify your configurati on by displaying the pending co nfiguration.
Step 7 exit Apply all ch ange s, and retu rn to global configuratio n mode.
Step 8 spanning-tree mode mst Enable MSTP. RSTP is also enabled.
Caution Changing sp an ning- tre e mo de s can d isrupt tra ffic because al l
spanning-tree instances are stopped for the previous mode and
restar ted in the new mode.
You cannot run both MSTP and PVST at the same time .
Step 9 end Return to privileged EXEC mode.
Step 10 show running-config Verify your entries.
Step 11 copy running-config startup-config (Optional) Save your entries in the configuration file.