Cisco IE-3000-8TC Software Configuration Guide - Page 405
Specifying the MST Region Configuration and Enabling MSTP
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Chapter 19 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 VLANs run MSTP.) For more information, see the "Spanning-Tree Interoperability and Backward Compatibility" section on page 18-10. For information on the recommended trunk port configuration, see the "Interaction with Other Features" section on page 15-16. • 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 mapping) 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, all 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 between 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 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. • For configuration guidelines about UplinkFast and BackboneFast, see the "Optional Spanning-Tree Configuration Guidelines" section on page 20-10. 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 limit to the number of MST regions in a network, but each region can only support up to 65 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. Step 1 Step 2 Command configure terminal spanning-tree mst configuration Purpose Enter global configuration mode. Enter MST configuration mode. OL-13018-03 Cisco IE 3000 Switch Software Configuration Guide 19-15
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