In this article we are going to talk about VTP. VTP means Vlan Trunking Protocol. It is a Cisco proprietary protocol which operates over trunk links. It synchronizes the vlan databases of switches in the VTP domain.
What is a VTP domain? All the switches in a particular group should have configured the same VTP domain or else they do not synchronize the vlan databases.
VTP works with configuration revision number. VTP servers and clients synchronized to the latest or highest revision number. (VTP modes- servers, clients will be discussed below) Every switch emits VTP advertisements every five minutes and when there is a change like creation of a vlan, delete or update. This VTP advertisements are sent as multicast frames.
VTP has mainly 3 modes. They are as follows,
1. Server mode
- This is the default mode and have the access to create vlans and the vlans are shared with other modes.
2. Client mode
- In this mode, cannot create vlans but can access vlans created by server.
3. Transparent mode
- In this mode, do not get access for vlans created by server. They are able to create vlans but do not direct them to other modes.
We can check our VTP configuration by ‘show vtp status’ in privilege mode of the switch.
Server mode changes to client mode if the client has higher configuration revision number. If a new switch with client mode and higher revision number is added to the group, it distributes the incorrect vlan information within the group. To avoid this switch must reset revision number to 0.