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Igor M

Vtp Troubleshooting

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How do you debug vtp trunking? Lets say you are not pulling vlans from server on a client, the uplinks are all showing as trunking, vtp parameters are all a match, - I am looking for some debug commands that can help with seeing whats going on with trunking

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I had the exact same problem, on one of the IEWB labs.

 

I did sh vtp status on the server, check the number of vlans and the revision numbers. Do the same on the client. If they do not match, then their is disparity between the two. The few things that will prevent them from exchanging is

 

Version mismatch

Authentication, on one side not the other

A malformed trunk

 

So, strip off the authentication, code the version number and create a basic trunk. Back to basics is the key, once you take off the extra baggage it's amazing how quickly you get to solve the problem.

 

 

Good luck

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Exactly the problem I hit with one of the iewb labs, one of the switches would not pickup the vlans from the server. I went head over my feet trying to get it to sync, my labs are all dynamips run, so I did not know what to blame - the sim platform or the way the config is working out... I realize that there are peripheral checks that are out there to help you out, such as checksums, revisions etc. However, I was looking for something from 'debug' repertoire to see where the hiccups were happening. It ended up being a dynamips problem - once the client switches pickup the vlans from server, you do a write mem, - those vlans that the client had picked up are going to be there for good. If you restart the simulation, the clients would not be able to re-write vlan.db unless you wipe out the flash and re-sync them...

 

So I guess if you are faced with a trunking issue, as Dave mentioned, you really have to take the whole thing apart and rebuild from scratch... Its a pity there is no debugs for it

 

 

I had the exact same problem, on one of the IEWB labs.

 

I did sh vtp status on the server, check the number of vlans and the revision numbers. Do the same on the client. If they do not match, then their is disparity between the two. The few things that will prevent them from exchanging is

 

Version mismatch

Authentication, on one side not the other

A malformed trunk

 

So, strip off the authentication, code the version number and create a basic trunk. Back to basics is the key, once you take off the extra baggage it's amazing how quickly you get to solve the problem.

 

 

Good luck

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How do you debug vtp trunking? Lets say you are not pulling vlans from server on a client, the uplinks are all showing as trunking, vtp parameters are all a match, - I am looking for some debug commands that can help with seeing whats going on with trunking

 

Hi Igor,

 

You can debug VTP using the following "debug sw-vlan vtp events" & "debug sw-vlan vtp events packets"

 

Cheers,

 

Fred

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this might be interesting, thanks Fred!

 

How do you debug vtp trunking? Lets say you are not pulling vlans from server on a client, the uplinks are all showing as trunking, vtp parameters are all a match, - I am looking for some debug commands that can help with seeing whats going on with trunking

 

Hi Igor,

 

You can debug VTP using the following "debug sw-vlan vtp events" & "debug sw-vlan vtp events packets"

 

Cheers,

 

Fred

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Agreed...

 

I like to get all my stuff working THEN I put the password on.

 

So... Sort out L2, then put VTP password on, THEN put on PPP over FR etc.

 

Do L3 THEN authenticate links etc.

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Hi All,

 

I experianced exactly the same issue with the IEWB Lab.

What I tracked the issue to - was the STP root bridge for Vlan 1 (the native Vlan on the interswitch trunks).

The root bridge was SW4 - therefore from SW1 the links to SW3 (for Vlan 1) were all blocking.

 

This meant that VTP updates were not being sent out of these trunks. (discovered this thanks to the debug commands added by Fred - thanks)

 

I forced SW1 to be the root for Vlan 1 - problem solved.

 

Cheers

Lee

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