VTP

[Sinosha]

Can a vtp server sync its database with vtp clients if the vtp client has a higher version number? 

[marce1000]

 - The vtp server never syncs it's database with a client

 M.

[Sinosha]

Thank you, I just wanted to make sure, what can happen in these two situations?

Even if the Client: 

1. has the same domain name in the network, OR; 2. It has higher revision number than the server? 

[Joseph W. Doherty · Accepted solution]

"The vtp server never syncs it's database with a client"

I believe that's incorrect, at least with VTP versions 1 or 2.

[balaji.bandi]

VTP Server can add, modify, and delete VLANs. It will propagate a VTP message containing all the changes from all of its trunk ports. If the server receives a VTP message, it will incorporate the change and forward the message from all remaining trunk ports.

VTP client switch cannot change the VLAN configurations itself. It can only update its VLAN configuration through the VTP messages that it receives from VTP server. When it receives a VTP message, it incorporates with the change and then forwards it from remaining trunk ports.

This means VTP Server always pushes the information to VTP clients.

[Joseph W. Doherty]

"This means VTP Server always pushes the information to VTP clients."

For versions 1 and 2, it's not always.  The "classical" way to fall into a client sourcing a newer VLAN DB, is you have a lab VTP setup that "looks" like prod.  You then connect a VTP lab switch into the prod network.  As you note, VTP message go out from both VTP servers and clients, because clients act as a "relay".  So, a VTP lab switch, client, with a higher VLAN DB rev. number. will go out as the "best" VLAN database.

BTW, I actually "saw" a fortune 100 company trash their HQ LANs making exactly this mistake.

[balaji.bandi]

"Can a vtp server sync its database with vtp clients if the vtp client has a higher version number? "

But OP's question was only VTP Server and Clients, there is no 2 VTP Servers in the discussion here right?

or am I misreading your answer in a different way and interpreting in another way (apologies if that is the case).

[Joseph W. Doherty · Accepted solution]

"But OP's question was only VTP Server and Clients, there is no 2 VTP Servers in the discussion here right?"

Correct, but in my posting(s) I included a couple of situations on how VTP rev. 1/2 can get its VLAN databases out of sync across multiple switches.  I.e. for the update process (between switches), only VLAN database rev. number matters.  Switch's VTP role, server or client, doesn't matter.

"Can a vtp server sync its database with vtp clients if the vtp client has a higher version number?"

Yes it can (again for versions 1 and 2).  The VTP server will accept the client's higher version number and replace its VLAN databases with the one provided by the client.

"or am I misreading your answer in a different way and interpreting in another way (apologies if that is the case)."

Perhaps you are misreading and interpreting incorrectly, but more likely I'm not always clear conveying the point I'm trying to make.  (Oh, no need to apologize. I appreciate anyone who asks for clarification and/or points out an error, civilly.)

[Joseph W. Doherty]

In VTP versions 1 and 2, a client with a higher DB rev. will become the VLAN DB for the VTP domain.

Again, in VTP versions 1 and 2, what VTP server role allows is manual reconfiguration of the VLAN DB; which is not allowed on a VTP client.

BTW, introducing a client with a VTP DB with a higher rev. number is the "classic" way to mess up your LAN.  This "feature" is often why many don't want anything to do with VTP.  Also, however, VTP version 3 is a "different animal".

Another BTW issue with VTP versions 1 and 2, if you have more than one active VTP server, and someones make "same time" changes on different VTP servers (within same VTP domain), you may have two different versions of your VLAN database on different VTP servers and clients.  Another reason why many network engineers shun VTP.

There are other pitfalls easy to fall into too (again using VTP versions 1 or 2).

Personally, I like using it, but using it properly takes care.

[MHM Cisco World]

ver1 & 2 depend on revision number 
ver3 no only primary server can update VLAN

[anirbansbd]

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