yes

Okay, it used by VTP to keep track of the vlan database. So you have one of your switches as a VTP server and the rest are VTP clients. Assuming the VTP revision number is 0.

You add a new vlan on the VTP server switch and save the config. When you do this the VTP revision number is then incremented by 1 on the VTP server switch.

This VTP server switch then sends out a VTP update message to the other switches and these switches then check their revision number against the one in the VTP update message. The revision number in the update is 1 and the clients VTP revision number is 0 so they know they have received a message with a more up to date vlan database. So they update their own vlan database info based on the VTP message.

Each time a vlan is created/deleted/modfied on the VTP server the revision number is incremented on the VTP server.

Jon

And how I can be sure, that VTP client willn't become VTP server?

What useful commands can I use?

It won't become the VTP server unless you make it the VTP server ie. you would need to make the change yourself

switch(config)# vtp mode server

"sh vtp status" will show you the status of the switch.

One other thing. When adding a new switch to your network always make sure the revision number is 0 and that you have set the switch to be a VTP client (or transparent).

To ensure the revision number is 0 on the switch change the vtp mode to transparent and then back to client mode.

Jon

As I understood, I cann't see revision number by

default with some command?

You can see the configuration revision number with the following commands -

IOS based switch = "sh vtp status"

CatOS based switch = "sh vtp domain"

Jon