How VTP Works
VTP has three different modes of operation within a domain: Server, Client and transparent.
Every catalyst switch is a server by default. Every network or domain requires a server to propagate VLAN information throughout the network or domain.
As a server switch, it will be able to create, add and delete VLANs in the domain.
VTP server controls any change that’s to be made in the entire domain. When a change is made on the server, it will be advertised throughout the entire VTP domain. VTP server configurations are saved in the NVRAM.
Switches in a client mode receive information from VTP servers.
VTP client switches also send and receive updates, but one difference between clients and server is that; VTP client switches can’t create, change and delete VLANs. In other words, none of the ports on the client switch can be added to a new VLAN without the authorization or notification from the server switch.
Switches in client mode processes and forwards VLAN information. VLAN information on client switches is not saved in NVRAM.
Switches in this mode don’t take part in VTP domain or database. They behave more or less like servers in that they create, modify and delete VLANs because they have and keep their own databases, which is only locally important.
VTP switches in transparent modes only purpose in a VTP domain is to forward VTP advertisements through any configured trunk links.