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Cisco Systems IntelligentGigabit Ethernet Switch Modules for the IBMBladeCenter, Software Configuration Guide
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Chapter10 Configuring MSTP
Configuring MSTP Features
•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 11-10.
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 same MST configuration; each member
must be capable of processing RSTP BPDUs. There is no limi t to the number of MST regions in a
network, but each region can only support up to 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 c onfiguration and
enable MSTP. This procedure is required.
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 spanning-tree mst configuration Enter MST configuration mode.
Step3 instance instance-id vlan vlan-range Map VLANs to an MST instance.
•For instance-id, you can specify a single instance, a range of
instances separated by a hyphen, or a series of instances separated by
a comma. The range is 1 to .
•For vlan vlan-range, the range is 1 to 4094.
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.
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.
Step4 name name Specify the configuration name. The name string has a maximum length
of 32 characters and is case sensitive.
Step5 revision version Specify the configuration revision number. The range is 0 to 65535.
Step6 show pending Verify your configuration by displaying the pending configuration.
Step7 exit Apply all changes, and return to global configuration mode.