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Configuring VTP
Information About Configuring VTP
When a switch is in VTP server mode, you can change the VLAN configuration and have it propagated throughout
the network.
When a switch is in VTP client mode, you cannot change its VLAN configuration. The client switch receives VTP
updates from a VTP server in the VTP domain and then modifies its configuration accordingly.
When you configure the switch for VTP transparent mode, VTP is disabled on the switch. The switch does not send
VTP updates and does not act on VTP updates received from other switches. However, a VTP transparent switch
running VTP version 2 does forward received VTP advertisements on its trunk links.
VTP off mode is the same as VTP transparent mode except that VTP advertisements are not forwarded.
Caution: If all switches are operating in VTP client mode, do not configure a VTP domain name. If you do, it is
impossible to make changes to the VLAN configuration of that domain. Therefore, make sure you configure at least
one switch as a VTP server.
VTP Advertisements
Each switch in the VTP domain sends periodic global configuration advertisements from each trunk port to a reserved
multicast address. Neighboring switches receive these advertisements and update their VTP and VLAN configurations
as necessary.
VTP advertisements distribute this global domain information:
VTP domain name
VTP configuration revision number
Update identity and update timestamp
MD5 digest VLAN configuration, including maximum transmission unit (MTU) size for each VLAN
Frame format
VTP advertisements distribute this VLAN information for each configured VLAN:
VLAN IDs (IEEE 802.1Q)
VLAN name
VLAN type
VLAN state
Additional VLAN configuration information specific to the VLAN type
In VTP version 3, VTP advertisements also include the primary server ID, an instance number, and a start index.
VTP Version 2
If you use VTP in your network, you must decide which version of VTP to use. By default, VTP operates in version 1.
VTP version 2 supports these features that are not supported in version 1:
Token Ring support—VTP version 2 supports Token Ring Bridge Relay Function (TrBRF) and Token Ring Concentrator
Relay Function (TrCRF) VLANs. For more information about Token Ring VLANs, see Normal-Range VLANs, page 273.
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 when the switch is
operating in VTP server mode.
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