Cisco Cisco IOS Software Release 12.2(55)SE

Support for any database in a domain. In addition to propagating VTP information, version 3 can 
propagate Multiple Spanning Tree (MST) Protocol database information. A separate instance of 
VTP runs for each application that uses VTP.

VTP primary and secondary servers. A VTP primary server updates the database information and 
sends updates that are honored by all devices in the system. A VTP secondary server can back up in 
NVRAM only the updated VTP configurations received from the primary server. 

By default, all devices come up as secondary servers. You can enter the vtp primary privileged 
EXEC command to specify a primary server. Primary server status is only needed for database 
updates when the administrator issues a takeover message in the domain. You can have a working 
VTP domain without any primary servers. Primary server status is lost if the device reloads or 
domain parameters change, even when a password is configured on the switch.

The option to turn VTP on or off on a per-trunk (per-port) basis. You can enable or disable VTP per 
port by entering the [no] vtp interface configuration command. When you disable VTP on trunking 
ports, all VTP instances for that port are disabled. You cannot disable VTP for the MST database 
and enable it for the VLAN database on the same port.

Globally setting VTP mode to off applies to all the trunking ports in the system. However, you can 
specify on or off per-VTP instance. For example, you can configure the switch as a VTP server for 
the VLAN database but with VTP off for the MST database.

VTP version 2 and version 3 are disabled by default. 

VTP mode is the same as VTP version 1 or 2 mode before conversion to VTP 3.

VTP v3 server type is secondary.

Follow these guidelines when deciding which VTP version to implement:

All switches in a VTP domain must have the same domain name, but they do not need to run the 
same VTP version.

Do not enable VTP version 2 on a switch unless all of the switches in the same VTP domain are 
version-2-capable. When you enable version 2 on a switch, all of the version-2-capable switches in 
the domain enable version 2. A version 1-only switch does not exchange VTP information with 
switches that have version 2 enabled.

VTP version 1 and VTP version 2 are not interoperable on switches in the same VTP domain. Do not 
enable VTP version 2 unless every switch in the VTP domain supports version 2.

A VTP version 2-capable switch can operate in the same VTP domain as a switch running VTP 
version 1 if version 2 is disabled on the version 2-capable switch. (Version 2 is disabled by default.)

If a switch running VTP version 1 but capable of running VTP version 2 receives VTP version 3 
advertisements, it automatically moves to VTP version 2.

If a switch running VTP version 3 is connected to a switch running VTP version 1, the VTP version 
1 switch moves to VTP version 2, and the VTP version 3 switch sends scaled-down versions of the 
VTP packets so that the VTP version 2 switch can update its database. 

A switch running VTP version 3 cannot move to version 1 or 2 if it has extended VLANs.