4.7 VTP Configuration
4.7.2 Configure the VTP version
Two different versions of VTP can run in your management domain, VTP Version 1 and VTP Version 2. The two versions are not interoperable. If you choose to configure a switch in a domain for VTP Version 2, you must configure all switches in the management domain to be in VTP Version 2. VTP Version 1 is the default. You may need to implement VTP Version 2 if you need some of the specific features that VTP Version 2 offers that are not offered in VTP Version 1. The most common feature that is needed is Token Ring VLAN support.

To configure the VTP version on a Cisco IOS command-based switch, you must first enter VLAN database mode. From there, you can set the VTP version as shown in Figure . In this example, VTP Version 2 has been configured.

Use the following command to change the VTP version number on a set command-based switch.

Switch (enable) set vtp v2 enable

VTP Version 2 supports the following features not supported in Version 1:

  • Token Ring support - VTP Version 2 supports Token Ring LAN switching and VLANs.
  • Unrecognized type/length/value (TLV) support - A VTP server or client propagates configuration changes to its other trunks, even for TLVs it is not able to parse. The unrecognized TLV is saved in NVRAM.
  • Version-dependent transparent mode - In VTP Version 1, a VTP transparent switch inspects VTP messages for the domain name and version, and forwards a message only if the version and domain name match. Because only one domain is supported in the supervisor engine software, VTP Version 2 forwards VTP messages in transparent mode without checking the version.
  • Consistency checks - In VTP Version 2, VLAN consistency checks (such as VLAN names and values) are performed only when you enter new information through the command-line interface (CLI) or Simple Network Management Protocol (SNMP). Consistency checks are not performed when new information is obtained from a VTP message, or when information is read from NVRAM. If the digest on a received VTP message is correct, its information is accepted without consistency checks. A switch that is capable of running VTP Version 2 can operate in the same domain as a switch running VTP Version 1 if VTP Version 2 remains disabled on the VTP Version 2-capable switch.
  • If all switches in a domain are capable of running VTP Version 2, you need to enable VTP Version 2 on only one switch (using the set vtp v2 enable command). The version number is propagated to the other VTP Version 2-capable switches in the VTP domain.