White Papers

1. Enable MSTP globally and set the region name and revision map MSTP instances to the VLANs.
2. Assign Layer-2 interfaces to the MSTP topology.
3. Create VLANs mapped to MSTP instances tag interfaces to the VLANs.
(Step 1)
spanning-tree
spanning-tree configuration name Tahiti
spanning-tree configuration revision 123
spanning-tree MSTi instance 1
spanning-tree MSTi vlan 1 100
spanning-tree MSTi instance 2
spanning-tree MSTi vlan 2 200
spanning-tree MSTi vlan 2 300
(Step 2)
interface 1/0/31
no shutdown
spanning-tree port mode enable
switchport protected 0
exit
interface 1/0/32
no shutdown
spanning-tree port mode enable
switchport protected 0
exit
(Step 3)
interface vlan 100
tagged 1/0/31
tagged 1/0/32
exit
interface vlan 200
tagged 1/0/31
tagged 1/0/32
exit
interface vlan 300
tagged 1/0/31
tagged 1/0/32
exit
Debugging and Verifying MSTP Configurations
To debut and verify MSTP configuration, use the following commands.
● Display BPDUs.
EXEC Privilege mode
debug spanning-tree mstp bpdu
● Display MSTP-triggered topology change messages.
debug spanning-tree mstp events
To ensure all the necessary parameters match (region name, region version, and VLAN to instance mapping), examine your
individual routers.
To show various portions of the MSTP configuration, use the show spanning-tree mst commands.
To view the overall MSTP configuration on the router, use the show running-configuration spanning-tree mstp in
EXEC Privilege mode.
To monitor and verify that the MSTP configuration is connected and communicating as desired, use the debug spanning-
tree mstp bpdu command.
Key items to look for in the debug report include:
● MSTP flags indicate communication received from the same region.
○ As shown in the following, the MSTP routers are located in the same region.
542
Multiple Spanning Tree Protocol (MSTP)