VTP revision numbers

[Jamie Hancock]

Hi,

I have proved myself utterly wrong in the advice I gave to a colleague.

He had a consultant setup his network for him. Unfortunately, the guy setup the core (4510) in transparent mode. All the edge switches are setup as clients.

My colleague asked what would happen if he put the core into server mode. Even though the clients have a higher revision number I thought that there was no way a client could update the server.

I set a dev network up to replicate the environment, and, behold when I changed the core from transparent mode to server, the edge switch that is in client mode, updated the core.

The only way I can see around this is to put all the edge switches into transparent mode, then change the core to server, and then go back to the edge switched and change them to clients.

Has anyone else had the same thing? Is there a better way to do this?

J.

[Peter Paluch]

Hi Jamie,

Your findings are correct. It does not matter whether a switch is in VTP Server or Client mode. Once it has a higher revision number, it will assert its VLAN database over the VTP domain.

Your suggestion about moving all switches to the VTP Transparent mode and then gradually start converting them to Server/Client is also correct. Alternatively, you could set a VTP password on the core server - if the password is different from the password defined on the VTP client switches, they will not communicate their VLAN databases. However, note that if the clients currently have a correct VLAN database and you wish to have the same database on the core switch then you may safely convert it into the VTP Server mode. Client switches will overwrite its VLAN database but actually that is what you want - to have the same VLAN database throughout the network.

Best regards,

Peter