Cisco 3560G 48TS Software Configuration Guide - Page 335

Chapter 16 Configuring MSTP Configuring MSTP Features • 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. 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. Step 1 Step 2 Step 3 Command configure terminal spanning-tree mst configuration instance instance-id vlan vlan-range Step 4 name name Step 5 Step 6 Step 7 revision version show pending exit Purpose Enter global configuration mode. Enter MST configuration mode. 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 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. 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. 78-16156-01 Catalyst 3560 Switch Software Configuration Guide 16-13