Multiple Spanning Tree Protocol | 645Enable Multiple Spanning Tree GloballyMSTP is not enabled by default. To enable MSTP:Verify that MSTP is enabled using the show config command from PROTOCOL MSTP mode, as shown inFigure 29-2.Figure 29-2. Verifying MSTP is EnabledWhen you enable MSTP, all physical, VLAN, and port-channel interfaces that are enabled and in Layer 2mode are automatically part of the MSTI 0.• Within an MSTI, only one path from any bridge to any other bridge is enabled.• Bridges block a redundant path by disabling one of the link ports.Add and Remove Interfaces• To add an interface to the MSTP topology, configure it for Layer 2 and add it to a VLAN. If youpreviously disabled MSTP on the interface using the command no spanning-tree 0, re-enable it usingthe command spanning-tree 0.• Remove an interface from the MSTP topology using the command no spanning-tree 0 command. Seealso Removing an Interface from the Spanning Tree Group on page 1054 for BPDU Filtering behavior.Create Multiple Spanning Tree InstancesA single MSTI provides no more benefit than RSTP. To take full advantage of MSTP you must createmultiple MSTIs and map VLANs to them.Create an MSTI using the command msti from PROTOCOL MSTP mode. Specify the keyword vlanfollowed by the VLANs that you want to participate in the MSTI, as shown in Figure 29-3.Step Task Command Syntax Command Mode1 Enter PROTOCOL MSTP mode. protocol spanning-tree mstp CONFIGURATION2 Enable MSTP. no disable PROTOCOL MSTPFTOS(conf)#protocol spanning-tree mstpFTOS(config-mstp)#show config!protocol spanning-tree mstpno disableFTOS#
