VTP domain name change to null

[azi]

Hi,

I need to change the VTP domain name on one of my C2960 switches from a specific name to null. How can I do that? Will doing so cause the switch to loose connection to other switches connected to this switch?

Thanks, Azriel

[Brandon Buffin]

To my knowledge the only way to change back to NULL is to delete vlan.dat and reload the switch. Not a great option. You can type "vtp domain null" to change the name to "null". This is different than setting back to the default NULL. You should not lost connectivity, however the other switches will stop receiving VTP updates until you update the domain name.

Brandon

[azi]

Thanks Brandon,

Do you think it is better to just deleting the vlan.dat and reloading the switch in order to create a local VLAN on that switch?

Thanks,

Azriel

[Brandon Buffin]

So, you're trying to create a VLAN on the VTP server that will not propagate to the rest of the network? You can disable VTP on the server, change the name of the domain or delete vlan.dat and reload. Are you going to need to propagate VLANs again in the future? If so, this new local VLAN will be pushed out as well.

Brandon

[Julio E. Moisa]

Hi

If you execute:

delete flash:vlan.dat

you will erase the entire vlan database, and to take effect you must restart the switch as Brandon mentioned. 

If you want to turned off the VTP, there are some switch models that allow this command:

vtp mode off.

[Joseph W. Doherty]

Could you better describe what you're trying to accomplish?  Are you trying to have both VTP shared VLANs and a VLAN only know to one device?

[azi]

I am trying to create a local VLAN for a voice server and phones on one switch in a remote location which has the same domain name as the main campus. The remote location is connected to the main campus via fiber. I don't need this VLAN on the main campus.

The VTP domain name on the remote switch is the same as on the main campus and the VTP operation mode on the remote location switch is client.

[Julio E. Moisa]

Yeap the remote switch could be on transparent mode, but in a future you will have to create the vlans manually on that remote switch.

[Joseph W. Doherty]

You note you don't need this VLAN(s?) on the main campus.  Does the remote site need other site(s) VLAN(s)?

VTP shares VLAN information, but you can prune what VLANs are allowed up and down a trunk.

As far as I know, VTP does not support selective sharing of VLAN information for VTP devices within the same VTP domain.  In fact, the point of a VTP domain is to share VLAN information.  Again, though, VLAN data distribution can be controlled.

Conversely, VTP VLAN information sharing can be blocked by non-trunk ports, or different VTP domain names (or different VTP passwords), or VTP off mode while VLANs span VTP domains.

If you're attempting to selectively share VLAN information within the same VTP domain, I believe you'll find that contrary to the design purpose of VTP.

Setting a switch's VTP domain to null only sets it to automatically accept a VTP neighbor's defined VTP domain name.  Once the VTP domain has been set or accepted, if you wish to change it, you need to manually configure the update.

[abdqr]

First you have to change the VTP mode to Transparent. Then delete the vlan.dat file from flash and reload the switch