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Chapter 15
Configuring MSTP
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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.
Command
Step 1
configure terminal
Step 2
spanning-tree mst configuration
Step 3
instance instance-id vlan vlan-range
Step 4
name name
Step 5
revision version
Step 6
show pending
Step 7
exit
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of the MST regions must contain the CST root, and all of the other MST regions must have a better
path to the root contained within the MST cloud than a path through the PVST+ or rapid-PVST+
cloud. You might have to manually configure the switches in the clouds.
Partitioning the network into a large number of regions is not recommended. However, if this
situation is unavoidable, we recommend that you partition the switched LAN into smaller LANs
interconnected by routers or non-Layer 2 devices.
Purpose
Enter global configuration mode.
Enter MST configuration mode.
Map VLANs to an MST instance.
To specify a VLAN range, use a hyphen; for example, instance 1 vlan
1-63 maps VLANs 1 through 63 to MST instance 1.
To specify a VLAN series, use a comma; for example, instance 1 vlan 10,
20, 30 maps VLANs 10, 20, and 30 to MST instance 1.
Specify the configuration name. The name string has a maximum length
of 32 characters and is case sensitive.
Specify the configuration revision number. The range is 0 to 65535.
Verify your configuration by displaying the pending configuration.
Apply all changes, and return to global configuration mode.
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For instance-id, the range is 1 to 15.
For vlan vlan-range, the range is 1 to 4094.
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When you map VLANs to an MST instance, the mapping is
incremental, and the VLANs specified in the command are added to
or removed from the VLANs that were previously mapped.
Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
Configuring MSTP Features
15-13
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