Introduction to VTP (VLAN Trunking Protocol)

Hello Chris

Initially, a switch will have the following default parameters for VTP:

  • VTP operating mode: Server
  • VTP Domain Name: Null

In such a case, VTP is active, but switches will not actively create any VTP associations with any other switches simply because the domain has not been configured. When all switches have a domain of NULL, it is as if VTP is not functioning.

However, this can still be a dangerous situation, because if a rogue switch is added which has a VTP domain configured, it will start to send VTP messages, and any switch on the network that still has a NULL domain, will automatically adopt that domain as well.

You can’t disable VTP as a feature, but you can ensure that a switch never participates in any VTP domain that may appear on the network by simply changing the VTP mode to transparent like so:

Switch(config)#vtp mode transparent

This ensures that any VTP messages received will be ignored.

I hope this has been helpful!