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.
VTP Configurations
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.