Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Bronze

MST Boundary Problems

I'm at a loss, I have spent a few hours looking at my spanning-tree and I cannot figure out why my ports are showing "Bound (RSTP)".

Configurations match across the board, same VLAN's, same VLAN names, same revision number, same MST name, what am I missing?

Dist A:

spanning-tree mode mst

spanning-tree loopguard default

spanning-tree portfast bpduguard default

spanning-tree portfast bpdufilter default

spanning-tree extend system-id

!

spanning-tree mst configuration

name SIS

revision 1

instance 1 vlan 1-3, 173-174, 200-201, 2005

instance 10 vlan 1011-1019

instance 20 vlan 1021-1029

instance 30 vlan 1031-1039

instance 40 vlan 1041-1049

instance 50 vlan 1051-1059

instance 60 vlan 1061-1069

instance 70 vlan 1071-1079

instance 80 vlan 1081-1089

instance 90 vlan 1091-1099

!

spanning-tree mst 0-1,10,20,30,40,50,60,70,80,90 priority 24576

VTP Version : running VTP2

Configuration Revision : 0

Maximum VLANs supported locally : 1005

Number of existing VLANs : 8

VTP Operating Mode : Transparent

VTP Domain Name : SIS

VTP Pruning Mode : Disabled

VTP V2 Mode : Enabled

VTP Traps Generation : Enabled

Dist B:

spanning-tree mode mst

spanning-tree loopguard default

spanning-tree portfast bpduguard default

spanning-tree portfast bpdufilter default

spanning-tree extend system-id

!

spanning-tree mst configuration

name SIS

revision 1

instance 1 vlan 1-3, 173-174, 200-201, 2005

instance 10 vlan 1011-1019

instance 20 vlan 1021-1029

instance 30 vlan 1031-1039

instance 40 vlan 1041-1049

instance 50 vlan 1051-1059

instance 60 vlan 1061-1069

instance 70 vlan 1071-1079

instance 80 vlan 1081-1089

instance 90 vlan 1091-1099

!

spanning-tree mst 0-1,10,20,30,40,50,60,70,80,90 priority 28672

VTP Version : running VTP2

Configuration Revision : 0

Maximum VLANs supported locally : 1005

Number of existing VLANs : 8

VTP Operating Mode : Transparent

VTP Domain Name : SIS

VTP Pruning Mode : Disabled

VTP V2 Mode : Enabled

VTP Traps Generation : Enabled

Random Closet:

spanning-tree mode mst

spanning-tree loopguard default

spanning-tree portfast bpduguard default

spanning-tree portfast bpdufilter default

spanning-tree extend system-id

!

spanning-tree mst configuration

name SIS

revision 1

instance 1 vlan 1-3, 173-174, 200, 2005

instance 10 vlan 1011-1019

instance 20 vlan 1021-1029

instance 30 vlan 1031-1039

instance 40 vlan 1041-1049

instance 50 vlan 1051-1059

instance 60 vlan 1061-1069

instance 70 vlan 1071-1079

instance 80 vlan 1081-1089

instance 90 vlan 1091-1099

VTP Version : running VTP2

Configuration Revision : 0

Maximum VLANs supported locally : 1005

Number of existing VLANs : 8

VTP Operating Mode : Transparent

VTP Domain Name : SIS

VTP Pruning Mode : Disabled

VTP V2 Mode : Enabled

VTP Traps Generation : Disabled

The ports are completely mix-matched, Dist A to any closet shows fine, but any closet to Dist A show "Bound (RSTP)".

Dist B to any closet shows "Bound (RSTP)" and any closet to Dist B shows fine...

I attached a diagram to help with the visual. The red arrows indicate a Boundary problem and the direction, green arrows show proper MST boundary. You can see the boundary flows one way, I didn't mark ever connection, but they are all the same.

Thanks,

Craig

I attached a diagram to help with the visualization.

1 ACCEPTED SOLUTION

Accepted Solutions

Re: MST Boundary Problems

In random closet config, I see vlan 201 being mapped to instance 0 instead of instance 1 in dist A & B.

You can use the command "show spanning-tree mst configuration digest" to see the configuration digest sent in MST BPDUs. That's probably simpler to compare the MD5 digests when you have a large configuration, rather that checking them one line at a time;-)

HTH,

Francois

3 REPLIES

Re: MST Boundary Problems

In random closet config, I see vlan 201 being mapped to instance 0 instead of instance 1 in dist A & B.

You can use the command "show spanning-tree mst configuration digest" to see the configuration digest sent in MST BPDUs. That's probably simpler to compare the MD5 digests when you have a large configuration, rather that checking them one line at a time;-)

HTH,

Francois

Bronze

Re: MST Boundary Problems

That is why you passed your lab and I didn't :) Thanks for the second set of eyes and the "show spanning-tree mst configuration digest" command!

Craig

Re: MST Boundary Problems

I can remember a case escalated from the TAC, where no-one could see the difference between two regions. I was so desperate that I ended sniffing the BPDUs exchanged to check if they were correctly formed. There was a difference in the region name that I could only see because the sniffer output was in hexadecimal. For some reason, my brain just couldn't read the difference between the two region names even after checking 20 times. And so did a good 10 engineers before me. We should not overestimate the capability of the human race at comparing MST configurations, don't take it personally;-)

398
Views
0
Helpful
3
Replies
CreatePlease to create content