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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
mapping, the same configuration revision number, and the same name.
A region can have one member or multiple members with the same MST configuration; each member
must be capable of processing RSTP BPDUs. There is no limit to the number of MST regions in a
network, but each region can support up to 16 spanning-tree instances. You can assign a VLAN to only
one spanning-tree instance at a time.
Beginning in privileged EXEC mode, follow these steps to specify the MST region configuration and
enable MSTP. This procedure is required.
To return to the default MST region configuration, 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 configuration command. To return to the default name, use the no name MST
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
spanning-tree mst configuration Enter MST configuration mode.
Step 3
instance instance-id vlan vlan-range Map VLANs to an MST instance.
• For instance-id, the range is 1 to 15.
• For vlan vlan-range, the range is 1 to 4094.
When you map VLANs to an MST instance, the mapping is incremental,
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 through 63 to MST instance 1.
To specify a series, use a comma; for example, instance 1 vlan 10, 20, 30
maps VLANs 10, 20, and 30 to MST instance 1.
Step 4
name name Specify the configuration name. The name string has a maximum length
of 32 characters and is case sensitive.
Step 5
revision version Specify the configuration revision number. The range is 0 to 65535.
Step 6
show pending Verify your configuration by displaying the pending configuration.
Step 7
exit Apply all changes, and return to global configuration mode.
Step 8
spanning-tree mode mst Enable MSTP. RSTP is also enabled.
Caution Changing spanning-tree modes can disrupt traffic because all
spanning-tree instances are stopped for the previous mode and
restarted 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.