VTP3 vs VTP2

Unanswered Question
Feb 5th, 2009

I've downloaded and installed 12.2(33)SXI on a WS-SUP720-10G with the objective of migrating to VTP3 in order to turn off VTP on a per-trunk basis.

The rest of the network runs 12.2(33)SXH on WS-SUP720-3B using VTP2. In testing mode, these are standalone supervisors.

The documentation states that all devices in a VTP domain must run the same VTP version. In contradiction to this, there is also a section explaining the interaction between VTP V3 and V2 devices. (http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SX/configuration/guide/vtp.html) I've set up VTP3 as the primary server, and configured a VTP domain and no password. On the switch running 12.2(33)SXH, I've configured it as a VTP client using V2 and configured the same VTP domain and no password. The client is not sending or receiving Configuration Revisions when a vlan is added to the domain throught the VTP 3 primary server. I set the vtp server to use VTP2, but the client is still not sending or receiving configuration revisions (the count is not incrementing.)

Any ideas?

I have this problem too.
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Edison Ortiz Thu, 02/05/2009 - 06:23

Please post the show vtp status and show int trunk output.




Edison Ortiz Thu, 02/05/2009 - 15:20


One thing I see is the VTP Client having 11 existing Vlans, how those Vlans were created? When the switch was configured as VTP transparent or server?

One way to fix this, delete the vlan.dat from flash and reload the switch. It will automatically receive the VTP information from the current VTP server via the trunk switchports. It will also set itself to VTP server so you will need to change it again to VTP client but at that point, all Vlans are migrated.




bgorrell Fri, 02/06/2009 - 06:30

I'll try deleting the vlan.dat file. That's a good idea. My two issues are: can I have a vtp3 server in a vtp2 domain (which fails for me although the documentation states it is possible) and why isn't the config revision incrementing on the client when I turned vtp3 into a vtp2 server. Maybe deleting the vlan.dat file and restarting will fix this.

The 11 vlans were created when I configured device vtp2 from client to transparent modes. I was attempting to validate that I could still create vlans and that the conf revision number was not incrementing. I would then create a new vlan (ex vlan 3 in the posting) on the vtp server (vtp3) and then check device vtp2 to verify that the conf rev number had not incremented.

Edison Ortiz Fri, 02/06/2009 - 06:45

As you created the database originally in transparent mode, I wonder if the VTP server is unable to overwrite that file for some reason.

Please delete the vlan.dat as I suggested and post back with results.




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bgorrell Fri, 02/06/2009 - 08:27

The database was orginally created on device vtp3 using VTP version 3 in server mode. I was chaning device vtp2 from client to transparent mode to verify that the vlans could be created.

I deleted the vlan.dat file on both devices vtp2 and vtp3. I configured the vtp server for vtp version 2 on device vtp3 and added a vlan. Device vtp2 is in client mode running vtp version 2 and it will not receive a configuration revision update. I've include the config files of both devices.

bgorrell Fri, 02/06/2009 - 09:14

Oops. Thanks. It looks like deleting the vlan.dat file was what I needed to do. The client is receiving configuration revision updates.

Do you know if VTP version 3 is compatible with VTP version 2? (I've contradictory information in the configu guide.) If so, what do I need to modify to force the vtp version 2 client to receive updates from the vtp version 3 server?

Edison Ortiz Fri, 02/06/2009 - 09:18

The VTP version 3 is backward compatible with VTP version 2.

Enabling VTP version 3 in a server will allow the server to use the new features that came with VTP version 3 on others VTPv3 enabled devices while communicating with VTPv2 devices in VTPv2 mode.




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bgorrell Fri, 02/06/2009 - 09:20

I can't get it to work. This is the issue that started this thread. Do you have a sample config?

Edison Ortiz Fri, 02/06/2009 - 09:26

No, I do not. I suggest you open a TAC Case and work with them on duplicating your scenario.

One thing to keep in mind, don't force the VTP Server to run in V3 mode only. It must be able to communicate in VTP mode 2 for those VTPv2 clients/servers.



Leo Laohoo Thu, 02/05/2009 - 14:30

"configured a VTP domain and NO password"

VTP Domain and VTP Password must be the same before VLAN database will propagate.

By the way: Good idea setting up the 2nd one as a client. :)

bgorrell Fri, 02/06/2009 - 06:19

Aren't the passwords the same if no passwords are configured? In our current VTP2 environment we have only the VTP domain name configured. The VTP domain name is configured on both of these devices.

bshoebottom Thu, 03/18/2010 - 08:39

I realise this thread is over a year old, but it's still unanswered and I wanted to share my experiences/findings.

You may notice that switching your VTP2 server to VTP3 will reset the configuration revision to 0.   VTP2 is programmed to update the local database only if this config revision is greater in the received update.  In testing I created and subsequently removed VLANs from the VLAN database on the new VTP3 server, no need to create the SVIs, until the config revision was greater then the former VTP2 domain.  Only after this would my downstream VTP2 devices process the updates coming from the VTP3 server.

Hope this helps anyone that is still listening.


lamav Thu, 03/18/2010 - 09:47

Glad you found what you're looking for. IMHO, you are wasting your time worrying about the minute details of a near-worthless technology. VTP creates more problems than it resolves and I would never recommend using it - ever. If one needs to span a VLAN across so many switches that configuring each switch individually is too much work, then the person is either lazy or the VLAN's domain is way too wide for best practices.

Just my opinion...


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