VTP propagation

Unanswered Question
Feb 3rd, 2008

Hi all,


I have the following configuration.


Cisco Router 2811 [Router_A] <-> 2960 Switch [Switch_B] <-> 2960 Switch [Switch_C] <-> Cisco Router 2811 [Router_D] <-> 2960 Switch [Switch_E] <-> Hosts [Host_F].


Now, the Switch_B is configured in VTP Server mode and Switch_C and E in client modes. The interface between Switch_B & Switch_C are in trunk mode. I have also created a three VLANs, 100, 200, and 300 on Switch_B.



However, when I check the VTP status [by using show VTP status] on [Switch_C], it does not show the domain name nor does it show any of the VLANs from the switch configured as a server. I.e. the information is not being propagated.


Any advice would be highly appreciated.


Thanks.


Kind regards.


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Overall Rating: 5 (4 ratings)
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Kevin Dorrell Sun, 02/03/2008 - 11:18

The VTP information will not be propagated from B to C until certain parameters have been set up. In particular, they must be manually set up with the same domain name and password (if you have one). The password is case sensitive. In addition, you have to have a direct trunk between the two switches, but I think you have that already.


Also, the VLAN database will only be propagated if the server has a higher configuration revision number (which you can see with show vtp status) than the client.


Once those conditions are met, the VLAN list should propagate OK. (But not through your router.)


The only exception is when you take a brand new switch with a blank configuration and no VTP domain name and attach it to an existing VTP domain. In that case, and only in that case, the new switch can learn the domain name from the existing domain.


Kevin Dorrell

Luxembourg


network_enginee... Sun, 02/03/2008 - 11:32

Hi Kevin,


Thanks. Although, my understanding was that the domain (and thus the name) would also be propagated.


Brings me to another question: Is it possible to have a switch configured as a server as part of and serving multiple domains? E.g. a switch from the core [backbone] propagating VTP information to two different sides that are not related, e.g. domain LEFT and domain RIGHT?


Thanks again.


Kind regards,

fahad.sheikh Sun, 02/03/2008 - 11:51

Not really.


What you can do in this scenario is on the trunk port allows the specific VLAN's to propogate.

Istvan_Rabai Sun, 02/03/2008 - 11:58

Hi Ben,


Kevin is probably away, this is why I'm answering your question:


A switch can be a member of one VTP domain only.


Cheers:

Istvan

bilousand Mon, 02/04/2008 - 11:07

Domain name is present in every VTP message and WILL be accepted if there is no password configured for domain AND new attached switch has factory default VTP domain which is empty string.

fernandezcarlos Tue, 02/05/2008 - 14:49

In case the the switch is not in default setup, look at MD5 digest. If they domain name is setup in new switch, MD5 on both switches HAVE to be the same or client will not accept VTP advertisements.

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