Administrator Guide

To monitor and verify that the MSTP conguration 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 ags 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 “Dierent Region”? If so, one of the key parameters is not
matching.
• MSTP Region Name and Revision.
– The congured name and revisions must be identical among all the routers.
– Is the Region name blank? That may mean that a name was congured on one router and but was not congured or was
congured dierently 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
congured on one router but not the others.
Dell#show run spanning-tree mstp
!
protocol spanning-tree mstp
name Tahiti
revision 123
MSTI 1 VLAN 100
MSTI 2 VLAN 200,300
no disable
“Same Region,” shown in bold in the following example shows that the MSTP routers are in a single region.
Dell#debug spanning-tree mstp bpdu
MSTP debug bpdu is ON
Dell#
4w0d4h : MSTP: Sending BPDU on Tengig 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 Tengig 2/21 :
ProtId: 0, Ver: 3, Bpdu Type: MSTP, Flags 0x78Same Region
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: 19, Bridge Id: 32768:0001.e8d5.cbbd
4w0d4h : INST 1: Flags: 0x78, Reg Root: 32768:0001.e806.953e, Int Root Cost: 0
Brg/Port Prio: 32768/128, Rem Hops: 19
INST 2: Flags: 0x78, Reg Root: 32768:0001.e806.953e, Int Root Cost: 0
Brg/Port Prio: 32768/128, Rem Hops: 19
The bold line in the following example shows that the MSTP routers are in dierent regions and are not communicating with each
other.
4w0d4h : MSTP: Received BPDU on TenGig 2/21 :
ProtId: 0, Ver: 3, Bpdu Type: MSTP, Flags 0x78Different Region
Multiple Spanning Tree Protocol (MSTP)
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