VLAN Trunking Protocol

VTP stands for VLAN Trunking Protocol and is a protocol for configuration and administration of VLANs in Cisco networks.

Operation

VTP is based on a domain concept and has three different switch modes:

• Client
• Server
• Transparent
• Off (see Cisco Weblink )

Only in server and transparent mode VLANs manually added, modified, or deleted on a switch. These changes in the local VLAN database are passed through a special command to all devices that are in the VTP domain on the trunks. In transparent mode, VTP advertisements are those passed to other switches. The switch itself does not respond to these advertisements. In client mode, the VLAN database of the switch can not be changed manually, the switch learns the VLAN configuration exclusively through the advertisements. Otherwise, a client switch behaves identical to a server switch (among others he also distributes its VLAN database in the domain).

Each VTP database contains a Configuration Revision Number. This number is incremented for each change. Receives a switch a VTP Advertisement with a higher revision number it accepts the received VLAN configuration, otherwise, the Advertisement will be ignored. This applies to both server and client switches, which can cause a mistake verbrachter in a domain client switch with a matching domain ID and high revision number can override the VLAN database throughout the domain.

When using the VTP VLANs can only be used from 1 to 1024. VTP supports currently do not support extended VLAN ( 1025-4096 ). Advertisements are sent every five minutes by default by a VTP server.

From the software versions

• IOS 12.2 (33 ) SXI ( Catalyst 65xx )
• IOS 12.2 ( 33r ) SRC3 ( Catalyst 76xx ) and
• CATOS version 8.7 ( 1 ) ( Catalyst 65xx )

Is possible, the use of VTP version 3. This also extended VLANs can be distributed. A change from version 2 to 3 is fail- free possible. Clients who speak only version 2, still supplied with replications in the range ≤ 1024.