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Catalyst 3750 SwitchSoftware Configuration Guide
OL-8550-09
Chapter14 Configuring VTP
Configuring VTP
VTP Version
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.
•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 (version2 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.
•Do not enable VTP version2 on a switch unless all of the switches in the same VTP domain are
version-2-capable. When you enable version2 on a switch, all of the version-2-capable switches in
the domain enable version 2. If there is a version 1-only switch, it does not exchange VTP
information with switches that have version 2 enabled.
•We recommend placing VTP version 1 and 2 switches at the edge of the network because they do
not forward VTP version 3 advertisements.
•If there are TrBRF and TrCRF Token Ring networks in your environment, you must enable VTP
version 2 or version 3 for Token Ring VLAN switching to function properly. To run Token Ring and
Token Ring-Net, disable VTP version 2.
•VTP version 1 and version 2 do not propagate configuration information for extended range VLANs
(VLANs 1006 to 4094). You must configure these VLANs manually on each device. VTP version 3
supports extended-range VLANs. You cannot convert from VTP version 3 to VTP version 2 if
extended VLANs are configured.
•When a VTP version 3 device trunk port receives messages from a VTP version 2 device, it sends a
scaled-down version of the VLAN database on that particular trunk in VTP version 2 format. A VTP
version 3 device does not send VTP version 2-formatted packets on a trunk unless it first receives
VTP version 2 packets on that trunk port.
•When a VTP version 3 device detects a VTP version 2 device on a trunk port, it continues to send
VTP version 3 packets, in addition to VTP version 2 packets, to allow both kinds of neighbors to
coexist on the same trunk.
•A VTP version 3 device does not accept configuration information from a VTP version 2 or version
1 device.
•Two VTP version 3 regions can only communicate in transparent mode over a VTP version 1 or
version 2 region.
•Devices that are only VTP version 1 capable cannot interoperate with VTP version 3 devices.
Configuration Requirements
When you configure VTP, you must configure a trunk port on the switch stack so that the switch can send
and receive VTP advertisements to and from other switches in the domain.
For more information, see the “Configuring VLAN Trunks” section on page13-16.