VLAN Trunking Protocol (VTP): is a Cisco proprietary protocol that propagates the definition of Virtual Local Area Networks (VLANs) to the neighboring L2 devices. To do this, VTP carries VLAN information to all the switches in a VTP domain. VTP advertisements are sent over trunks.
VTP has three modes:
- Server: Can Add, edit and remove VLANs and the changes will be applied to all VTP Clients.
- Client: Clients get their configuration from the VTP server and they cannot modify their VLAN Database.
- Transparent: they will forward VTP Server advertisements without applying it. Yet, it will have the availability to modify their VLAN Database.
Related commands:
Command | Effect |
S1(config)#Vtp mode [server | client | transparent | off] | Sets the VTP mode |
S1(config)#Vtp domain [domain name] | Sets the VTP domain |
S1#show vtp status | Shows the VTP Version, mode and configuration revision |
Configuration notes:
- VTP Domain must be the same and it is case sensitive.
- VTP Version must be the same.
- VTP Passwords must match.
- Trunk links must be up.
- VTP May remove certain VLANs, once a VLAN is removed assigned ports will go into inactive state.
VTP v3
VTP v3 is similar to the older versions of the protocol but it came to enable more features and address certain issue.
VTP v3 added the support for extended VLANs, Private VLANs and RSPAN VLANs synchronization; it also added the possibility to sync MST configuration.
VTP v3 added a VTP primary server functionality to addresses the previously mentioned issue when a new VTP enabled device is introduced to the environment.
the VTP primary server is the only switch that is allowed to create / remove VLANs across the environment.
