VTP

The VLAN trunking protocol (VTP) is a Cisco-proprietary protocol that provides a way to manage Cisco switches as a single group for VLAN configuration. It ease the burden of configuring individual VLANs on multiple switches. VTP defines a VTP management domain where Cisco switches in the domain have VTP enabled. With VTP, you can create a new VLAN on one switch, and have VTP spread the information and configure the same VLAN on all other switches in the same domain automatically.

Each switch in a VTP management domain must be configured in one of four possible VTP modes:

1. Server mode: A switch configured in server mode can be used to add, delete, and change VLANs within the VTP management domain. It is the default VTP mode. There must be at least one switch with server mode per VTP management domain. Changes in the server are passed to all other switches in the VTP management domain.
2. Client mode: A switch configured in client mode is the recipient of any changes within the VTP management domain, such as the addition, deletion, and modification of VLANs by a server mode switch. A switch in VTP client mode cannot make any change to VLAN information.
3. Transparent mode: A witch configured in transparent mode passes VTP updates received by switches in server mode to other switches in the VTP management domain, but does not process the contents of these messages. When individual VLANs are added, deleted, or changed on a switch running in transparent mode, the changes are local to that particular switch only, and are not passed to other switches within the VTP management domain.
4. Off: The option disable VTP completely on a switch, it is only available after COS version 7.1.1.

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