VTP Version 1 versus VTP Version 2

dgj1 · ‎05-30-2008

In various Cisco documentation, I have read that VTP version 1 and VTP version 2 are incompatible or inoperable when implemented in the same domain. I have recently started a new job and have discovered that both versions are implemented in the domain. Does anyone know what if any are the potential issues associated with a network environment configured this way, on the surface VTP appears to be working?

lamav · ‎05-30-2008

Is the VTP mode set to transparent?

If so, that MAY explain why the VTP versions peacefully coexist in the same domain: setting VTP to transparent mode effectively disables it.

Anyway, I think VTP is a lot more trouble than it is helpful. Get rid of it.

HTH

Victor

dgj1 · ‎05-30-2008

Not in transparent mode. Server and Client mode. As I mentioned I just started this job, and I would prefer to put everything in transparent - but unfortunately that is not the direction they want to go. My first assignment is to replace one of their cores which is a 6009 running CAT-OS and is the only VTP Server in the domain. It is running V2 but about half of the access switches are running V1. They are not pruning any vlans on the trunks, and all vlans are being propagated to all switches. I should also mention that this is not a 3 tier model, no distribution layer for the access switches. I'm just wondering if I need to be concerned with the VTP version differences as a part of the migration. Any further advice would be greatly appreciated. Thanks!

mahmoodmkl · ‎05-30-2008

Hi

I think u need to look at the show vtp status output,it displays that the device can support vtp version 2 but its not enabled.u need to look for the link vtp v2 mode=enabled or disabled.This is going to give u the proper idea of whats going on.

Thanks

Mahmood

darrenj · ‎05-31-2008

Agreed, please show us the output of 'show vtp status' from your VTP server and one of your VTP clients...

Opinions vary on the use of VTP. It does make life incredibly easy when adding, deleting VLANs, BUT it can also give you BIG problems if you are not careful.

Theres a story I heard about a technician who introduced an second-hand switch onto a network but it had a higher config revision than the existing VTP setup. Bad news. The old switch replaced ALL VLANs rendering the network useless. If your thinking of doing this, make sure your resume is up to date ;-)

Darren

dgj1 · ‎05-31-2008

Darren,

Please see my previous posting regarding the VTP status.

As far as the config revision number they all have the same revision number. I'm aware that with VTP when introducing a new switch the revision number needs to be lower or better yet set to 0 to avoid overwriting the VLAN database. It is interesting to note that when introducing a new core, I will also be replacing the only VTP Server in the domain. I believe that I may have to bring up the new core first as a VTP client with a lower revision number to allow the VLAN's to be propagated to it from the old 6009 Core, and then promote the VTP Operating Mode to Server before I can remove the old core. Or I guess I could promote another switch already in the domain to a Server, remove the old core and then bring up the new one.

I agree VTP can be a pain and must be approached carefully. That's why I'm inquiring about the VTP version variance.

dgj1 · ‎05-31-2008

Darren,

Please see posting to Mahood regarding the VTP status output.

As far as the config revision number they all have the same revision number. I'm aware that with VTP when introducing a new switch the revision number needs to be lower or better yet set to 0 to avoid overwriting the VLAN database. It is interesting to note that when introducing a new core, I will also be replacing the only VTP Server in the domain. I believe that I may have to bring up the new core first as a VTP client with a lower revision number to allow the VLAN's to be propagated to it from the old 6009 Core, and then promote the VTP Operating Mode to Server before I can remove the old core. Or I guess I could promote another switch already in the domain to a Server, remove the old core and then bring up the new one.

I agree VTP can be a pain and must be approached carefully. That's why I'm inquiring about the VTP version variance.

dgj1 · ‎05-31-2008

The show VTP status is how I discovered that half of switches were running VTP1 (VTP2 Capable), VTP V2 is Disabled. All VLAN's are being learned from the Server that is running VTP2.

My question pertains to the Cisco documentation that only indicates that the two versions are not compatible or inoperable. I'm trying to find out what doesn't work if they co-exist so I know whether the version must be changed to avoid potential problems. Note: All switches have the same Configuration Revision Number, so I am certain they are getting all the updates.

Thanks

dgj1 · ‎05-31-2008

Mahood,

The show VTP status is how I discovered that half of switches were running VTP1 (VTP2 Capable), VTP V2 is Disabled. All VLAN's are being learned from the Server that is running VTP2.

My question pertains to the Cisco documentation that only indicates that the two versions are not compatible or inoperable. I'm trying to find out what doesn't work if they co-exist so I know whether the version must be changed to avoid potential problems. Note: All switches have the same Configuration Revision Number, so I am certain they are getting all the updates.

Thanks

dgj1 · ‎05-31-2008

Sorry about the double postings. This is my first time using this forum. I didn't realize that when I edited a message it wasn't editing the original but creating an additional posting. Ooops!

dgj1 · ‎06-01-2008

I found this on the net pertaining to the versions:

There are three version of VTP so far. VTP Version 2 (V2) is not much different than VTP Version 1 (V1). The major difference is that VTP V2 introduces the support for Token Ring VLANs. If you are using Token Ring VLANs, you need to enable VTP V2. Otherwise, there is no reason to use VTP V2. VTP version 3 differs from earlier VTP versions in that it does not directly handle VLANs. VTP version 3 is a protocol that is only responsible for distributing a list of opaque databases over an administrative domain. When enabled, VTP version 3 provides the following enhancements to previous VTP versions:

Support for extended VLANs.

Support for the creation and advertising of private VLANs.

Improved server authentication.

Protection from the "wrong" database accidentally being inserted into a VTP domain.

Interaction with VTP version 1 and VTP version 2.

Provides the ability to be configured on a per-port basis.

Provides the ability to propagate the VLAN database andother databases.

Based on this recent finding - It looks like I may not need to worry about the version differences co-existing since they are working and only V2 appears to only pertain to Token Ring. Perhaps a better plan is to change to Version 3 at some point in the future.

Does anyone have anything to share on this subject?

bvsnarayana03 · ‎06-01-2008

Interesting!!!!

Can you paste the output of "sh vtp status" of the 2 switches that you suspect to be running different modes yet synchronising.

dgj1 · ‎06-12-2008

The VTP Status Information you requested is attached for your review. Thank you!