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New Member

VTP Configuration

Greetings

I have a Cisco 4006 Switch which is working as a VTP Server in my network and serving almost more than 40 VTP Client switches in my network. Due to hardware issue, I have to replace this switch with 2950 Switch on temporary basis but for at least two weeks.

Now is this possible that if i configure the 2950 as VTP Server with the same configuration as of Cisco 4006 than the switches those are working as VTP Clients will update their VTP information via this new 2950 switch?

Do I need to perform any additional thing in this regard?

Quick response will be highly appreciated.

With Regards

Mansoor

8 REPLIES
Purple

Re: VTP Configuration

Hi Mansoor,

Switches will prefer VTP information that has a higher revision number than what they have already. If you install a new switch into the network, there is a good possibility that the revision number of that switch will be less than that of the existing switches. If that is the case, the VLAN configuration of the new switch will be overwritten by that of the existing switches, even if the new switch is a VTP server and the rest of the switches are VTP clients.

While there may be other ways of doing this, one method that could work is for you to do the following:

- determine the current revision level of the client switches using 'show vtp status'

- artificially increase the revision number of the new 2950 switch before installing it into the network. One way to do this is to simply make changes to the VLAN database until the revision number is higher

- then, introduce the 2950 into the network

Hope that helps - pls do rate the post if it does.

Paresh

Re: VTP Configuration

Hi Paresh,

are you sure a switch configured as VTP server will be updated by VTP clients, if the revision number is lower? My idea was, that only servers send VTP updates, and clients just receive (or forward) them. Removing the 4006 first would leave no server and thus no switch with current VLAN information in the vlan.dat file. I would not like to run a network under this condition.

So the 2950 could be added to the network as VTP client (clears the vlan.dat), then converted to server, while the 4006 is still in place. The 2950 should then be updated by the 4006 to the latest revision and the 4006 could be removed (assuming it is still alive now).

Check the revision on the 4006 and the 2950 before and after adding it with "show vtp status".

Hope this helps! Regards, Martin

Re: VTP Configuration

Hello,

AFAIK, there is a limit of 64 VLANs on a 2950 switch. If that limit is reached, the switch changes to VTP transparent mode. So, before introducing the 2950 as a VTP server switch, make sure that the VLAN limitation does not give you problems...

Regards,

GNT

New Member

Re: VTP Configuration

There is no need to configure switch as client and then turn it on to be a server again. Just make sure the revision number on that switch is lower then on "live" server. Then attach 2950 into the network, make sure it has recieved updates (it will if the domain name match or wasn't change from NULL even though it's a server too), detach 4006, voila.

Purple

Re: VTP Configuration

The switch config will be overwritten by the clients if the revision number on the clients is higher than the new 2950 . Also as best practice it is advisable to have 2 servers in your network thus avoiding problems like this . If you have a larger switch still in the network you might be able to change that to a server temporarily which should have the up to date revision number.

New Member

Re: VTP Configuration

It will only if you attach it as client. That's why you should connect it to network as a server with the revision number lower then existed, preferably 0.

New Member

Re: VTP Configuration

change the mode to transparent and then back to server or change the vtp domain to something different to the current domain and then back to the original domain. This forces it to a revision # of zero.

New Member

Re: VTP Configuration

Thanks all of you for your comments.

Now let me summarize what can be the possible workarounds, please verify

1. If i change the revision number of 2950 to the higher number than current VTP revision number and introduce it as a server into the network, the switches will not update themselves from it or in other words this workaround may lead to some mis-configuration especially if we donot have any Server available on the Network as VTP Server.

2. The Workaround which is applicable as far as i understand. Make 2950 as VTP Server, Change its mode to transparent or change the name of vtp domain so that its revision number will become zero, than convert this switch to the Server mode. Once it will update its Database, we can remove the 4006 happily. The Clients will update themselves only with the 2950 Switch lateron for any update.

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