Solved: VTP protocol: Client synchronizing a server

Steph1963 · ‎08-17-2010

Hi,

I have read that a VTP client can synchronize a VTP server if the client Revision number is higher than the server.

If it is correct to assume that the only switch in a VTP domain to hold the VLAN database is the server, can we say that the VLAN information for a client is lost as soon as power down the switch. In that case, the only way I can see, this is probably where I am wrong, a client can update a server is if the switch has an higher revision number and is connected to a new VTP domain without being shut off.

Thanks for your help

Stephane

milan.kulik · ‎08-18-2010

Hi,

the VLAN information for a client is NOT lost as soon as power down the switch. It's still available in the vlan.dat file.

See

http://www.cisco.com/en/US/tech/tk389/tk689/technologies_tech_note09186a0080890613.shtml#topic7

for details of the "VTP bomb" well-known problem.

BR,

Milan

View solution in original post

kyukim · ‎08-17-2010

Hi,

Let's look at definition of server and client.

Server—In VTP server mode, you can create, modify, and delete VLANs and specify other configuration parameters, such as VTP version and VTP pruning, for the entire VTP domain. VTP servers advertise their VLAN configuration to other switches in the same VTP domain and synchronize their VLAN configuration with other switches based on advertisements received over trunk links. VTP server is the default mode.
Client—VTP clients behave the same way as VTP servers, but you cannot create, change, or delete VLANs on a VTP client.

You can see VTP client advertise their vlan configuration to other switches in VTP domain and sync with them. Only difference is that you can't create or change or delete vlans.

So, most of VTP version problem occurs when you introduce new switch that already has vlan database with higher revision no into existing VTP domain.

It is best practice to remember the configuration revision and how to reset it each time that you insert a new switch in your network so that you do not bring down the entire network.

http://www.cisco.com/en/US/tech/tk389/tk689/technologies_tech_note09186a0080094c52.shtml

KK.

milan.kulik · ‎08-18-2010

Hi,

the VLAN information for a client is NOT lost as soon as power down the switch. It's still available in the vlan.dat file.

See

http://www.cisco.com/en/US/tech/tk389/tk689/technologies_tech_note09186a0080890613.shtml#topic7

for details of the "VTP bomb" well-known problem.

BR,

Milan

Scott_O'Brien · ‎08-18-2010

Hi,

when a Client boots up it does send out a Summery Advertisement, so if the client switch has a higher revision number then the vtp server and is conected to the vtp domain and has a higher revision number then yes it will create a synchronize error, how ever this is very unlickly has the switch has to be conected to the network at boot up and have a higher revision number of the vtp server and be part of the vtp domain.

the best way to make sure a switch has its revision number set lower then the vtp server is:

1. you can join it to a fake domain and back to the real one then conect it to your network or

2. make it a transperent switch then back to client and join it to your network.

thanks

Scott O'Brien

Steph1963 · ‎08-23-2010

Hi,

Does erasing the client vlan.dat file would prevent the client from synchronizing the server and the rest of the VTP domain.

Thanks

Stephane