I currently have 5 Catalyst 3548XL switches connected through Gigastack modules that are the backbone of my LAN. They are setup in a VTP domain but changes are rarely, if ever, made.
I need to replace one of them with a new 3560 but the one I need to replace is the VTP server. What should I do?
Should I copy the config from the 3548 (can I even do that) and have this new 3560 set as a server when I connect it?
Should I set all the switches to VTP transparent mode? Will this cause an issue or wipe all the current config information on switches that are currently in VTP Client mode?
The horror story is if you introduce a new switch with a higher configuration revision number and it then overwrites the existing vlan database on all your live switches with it's own which is usually just vlan 1. The switch you introduce doesn't even have to be a VTP server, it can be a VTP client.
So the key thing is the configuration number. So i would do this
1) Your existing VTP server should have the correct vlan database.
2) Choose one of your other switches in the stack and change it from VTP client to VTP server. Before you do this check it has the same revision number as your existing VTP server but it should do as it is a live switch.
3) There is no need to demote your existing VTP server. You can have 2 VTP servers or more if you wish and most networks do have at least 2 VTP servers.
The new 3560. Before connecting it to the other switches log in and change it to VTP transparent then back to VTP client. This will set it's configuration revision number to 0 which is what you want.
Connect it to the other switches and let it get the VTP updates. Then it's up to you whether you leave it as a VTP client or promote it to a VTP server.
As i said before the key to all this is the revision number.
For reference if you have 2 VTP servers with the same revision number and you add another vlan for example on switch1 then switch1 will have the higher revision number and all the other switches, the VTP clients AND the other VTP server will update their databases with the new vlan as they will all have a lower configuration number.