Two versions of VTP, VTP version 1 and VTP version 2, are available for use in a management domain.
Although VTP version 1 is the default protocol on a Catalyst switch, Catalyst switches are capable of
running both versions; however, the two versions are not interoperable within a management domain. Thus,
the same VTP version must be configured on each switch in a domain. However, a switch running VTP
version 2 may coexist with other version 1 switches, if its VTP version 2 is not enabled. This situation
becomes important if you want to use version 2 in a domain. Then, only one server mode switch needs to
have VTP version 2 enabled. The new version number is propagated to all other version 2-capable switches
in the domain, causing them to enable version 2 for use. By default, VTP version 1 is enabled. Version 2 can
be enabled or disabled using the v2 option. The two versions of VTP differ in the features they support. VTP
version 2 offers the following additional features over version 1:
• In transparent mode VTP version 1 matches the VTP version and domain name before forwarding the
information to other switches using VTP. On the other hand, VTP version 2 in transparent mode
forwards the VTP messages without checking the version number.
• VTP version 2 performs consistency checks on the VTP and VLAN parameters entered from the CLI or
by Simple Network Management Protocol (SNMP). This checking helps prevent errors in such things as
VLAN names and numbers from being propagated to other switches in the domain. However, no
consistency checks are performed on VTP messages that are received on trunk links or on configuration
and database data that is read from NVRAM.
• VTP version 2 supports the use of Token Ring switching and Token Ring VLANs.
• VTP version 2 has Unrecognized Type-Length-Value (TLV) support, which means that VTP version 2
switches will propagate received configuration change messages out other trunk links, even if the switch
supervisor is not able to parse or understand the message.
On an IOS-based switch, the VTP version number is configured using the following commands:
Switch# vlan database Switch(vlan)# vtp v2-mode
On a CLI-based switch, the VTP version number is configured using the following command:
Switch(enable) set vtp v2 enable