Glossary
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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.
○ 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.
The following example shows the show run spanning-tree mstp command.
DellEMC#show run spanning-tree mstp
!
protocol spanning-tree mstp
name Tahiti
revision 123
MSTI 1 VLAN 100
MSTI 2 VLAN 200,300
The following example shows viewing the debug log of a successful MSTP configuration.
DellEMC#debug spanning-tree mstp bpdu
MSTP debug bpdu is ON
DellEMC#
4w0d4h : MSTP: Sending BPDU on Te 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
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Multiple Spanning Tree Protocol (MSTP)