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Cisco IE 2000 Switch Software Configuration Guide
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Chapter 18 Configuring VTP
Information About Configuring VTP
• VTP primary server and VTP 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 only back up the updated VTP configurations received from th e primary server to its NVRAM.
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 nee ded for database
updates when the administrator issues a t akeover 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 set VTP to off for the MST database
and on for the VLAN database on the same port.
When you globally set VTP mode to off, it applies to all the trunking ports in the system. However,
you can specify on or off on a per-VTP instance basis. 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 Guidelines
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 (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 VT P version 2.
• If a switch running VTP version 3 is connected to a switch running VTP version 1, t he 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 VLA Ns.
• 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. 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 4096). 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 f ormat. A VTP
version 3 device does not send VTP version 2-formatted packets on a trunk unless it first r eceives
VTP version 2 packets on that trunk port.