Introduction
VLAN Trunking Protocol (VTP) was created by Cisco but is not proprietary. The basic goals of VTP are to manage all configured VLANs across a switched internetwork and to maintain consistency throughout that network. VTP allows an administrator to add, delete, and remane VLANs. The modification information is propagated to all other switches in the VTP domain.
All switches who need to share VLAN information must use the same domain. A switch can be in only one domain at a time.
VTP modes:
Server: This is the default for all Catalyst switches. You need at least one server in your VTP domain to propagate VLAN information throughout the domain. The switch must be in server mode to be able to create, add, or delete VLANs in a VTP domain. Changing VTP information must also be done in server mode, and any change made to a switch in server mode will be advertised to the entire VTP domain.
Client: In client mode, switches receive information from VTP servers, and they also send and receive updates. But they can’t make any changes.
Transparent: Switches in transparent mode don’t participate in the VTP domain, but they’ll still forward VTP advertisements through any configured trunk links. These switches can’t add and delete VLANs because they keep their own database—one they do not share with other switches.
You may want to set a password so you can prevent users from adding switches to your VTP domain. If you set a password, it must be same in every switch.