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VTP revision number and VLAN database updates

Hi - Theoretically, is the following possible ?

We have an established network on VTP domain say - CORP where we have a core switch performing the VLAN/VTP updates.

Someone plugs in a rogue switch to the network - say configured for a different VTP domain TEST, or maybe just a default undefined VTP domain. If the VTP Revision number of the rogue switch is higher than the Core Switch(CORP) - can the rogue switch wipe out the VLANs on CORP ?

My understanding from VTP is that the server and client need to be on the same domain for updates to occur flowing from the Server to the Client. But, also read somewhere that VTP revision is more something that needs to be a watch out for.

In question would be a CAT 6506 being the Server, and the roque being any switch - even a Cisco 2940 which we might typically user for conference rooms.

pls advise

thanks in advance

  • Other Network Infrastructure Subjects
3 REPLIES
Purple

Re: VTP revision number and VLAN database updates

I thought they had to be in the same domain then if the new switch had a higher revision number it would overwrite the vtp database even if it is a client . the way to avoid this is to give the new switch a different domain name than the current then change it back to the right one and this will set the revision number back to 0.

Bronze

Re: VTP revision number and VLAN database updates

A switch if not configured for any vtp domain, defaulting to null, when plugged into a life network, it will join the domain that it learns about via vtp.

Also, a switch in vtp client mode, eventhough is not possible to configure vlan info on it, but will still propagate it's vlan d/b info via vtp. Therefore, if a client has a higher revision number then the one in the life network, therefore it will still wipe out the current VLANs in the life network replacing it with whatever that it has in it's own database.

There are 3 ways to avoid this:

1. Configure vtp mode of switch fr client to transparent, then switch it back to client mode. This will reset the vtp rev. back to 0.

2. Configure it to a different vtp domain, then switch it back. This will also reset the vtp rev. back to 0.

3. Configure ur switch uplink as an access port. VTP info will only propagate through trunks.

HTH.

Re: VTP revision number and VLAN database updates

In my Experience with the VTP things, I have also noticed that if you are introducing any switch in a VTP domain with a differnt domain name, the new switch will still join the VTP domain and it will be overwritten with the VTP config of the domain that it is joining and will have all the vlans and config revision number.

As posted above that if a client/server switch that you are introducing in your VTP domain with high revision number, it will still overwrite all the VTP info.

regards,

-amit singh

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