Reference Guide

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.
– Does the debug log indicate that packets are coming from a “Different Region”? If so, one of the key
parameters is not matching.
• MSTP Region Name and Revision.
– The configured name and revisions must be identical among all the routers.
– Is the Region name blank? That may mean that a name was configured on one router and but was not
configured or was configured differently on another router (spelling and capitalization counts).
• MSTP Instances.
– To verify the VLAN to MSTP instance mapping, use the show commands.
– Are there “extra” MSTP instances in the Sending or Received logs? This may mean that an additional
MSTP instance was configured on one router but not the others.
Example of Viewing MSTP Configuration
FTOS#show run spanning-tree mstp
!
protocol spanning-tree mstp
name Tahiti
revision 123
MSTI 1 VLAN 100
MSTI 2 VLAN 200,300
Example of Viewing the Debug Log (Successful MSTP Configuration)
FTOS#debug spanning-tree mstp bpdu
MSTP debug bpdu is ON
FTOS#
4w0d4h : MSTP: Sending BPDU on Gi 2/21 :
ProtId: 0, Ver: 3, Bpdu Type: MSTP, Flags 0x6e
CIST Root Bridge Id: 32768:0001.e806.953e, Ext Path Cost: 0
Regional Bridge Id: 32768:0001.e806.953e, CIST Port Id: 128:470
Msg Age: 0, Max Age: 20, Hello: 2, Fwd Delay: 15, Ver1 Len: 0, Ver3 Len: 96
Name: Tahiti, Rev: 123, Int Root Path Cost: 0
Rem Hops: 20, Bridge Id: 32768:0001.e806.953e
4w0d4h : INST 1: Flags: 0x6e, Reg Root: 32768:0001.e806.953e, Int Root Cost: 0
Brg/Port Prio: 32768/128, Rem Hops: 20
INST 2: Flags: 0x6e, Reg Root: 32768:0001.e806.953e, Int Root Cost: 0
Brg/Port Prio: 32768/128, Rem Hops: 20
4w0d4h : MSTP: Received BPDU on Gi 2/21 :
553