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Cisco IE 3010 Switch Software Configuration Guide
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Chapter 18 Configuring MSTP
Configuring MSTP Features
• The switch supports up to 65 MST instances. The number of VLANs that can be mapped to a
particular MST instance is unlimited.
• PVST+, rapid PVST+, and MSTP are supported, but only one version can be active at any time. (For
example, all VLANs run PVST+, all VLANs run rapid PVST+, or all VLAN s run MSTP.) For more
information, see the “Spanning-Tree Interoperability and Backward Compatibility” section on
page 17-10. For information on the recommended trunk port configuration, see the “Interaction with
Other Features” section on page 14-16.
• VTP propagation of the MST configuration is not supported. However, you can manually configure
the MST configuration (region name, revision number, and VLAN-to-instance map ping) on each
switch within the MST region by using the command-line interface (CLI) or through the SNMP
support.
• For load balancing across redundant paths in the network to work, a ll VLAN-to-instance mapping
assignments must match; otherwise, all traffic flows on a single link.
• All MST boundary ports must be forwarding for load balancing be tween a PVST+ and an MST
cloud or between a rapid-PVST+ and an MST cloud. For this to occur, the IST master of the MST
cloud should also be the root of the CST. If the MST cloud consists of multiple MST regions, one
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 pa th 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.
• For configuration guidelines about UplinkFast and BackboneFast, see the “Optional Spanning-Tree
Configuration Guidelines” section on page 19-10.
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 sam e MST configuration; each member
must be capable of processing RSTP BPDUs. There is no limit t o the number of MST regions in a
network, but each region can only support up to 65 spanning-tree inst ances. 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 Purpose
Step 1 configure terminal Enter global configuration mode.
Step 2 spanning-tree mst configuration Enter MST configuration mode.