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Cisco IE 2000 Switch Software Configuration Guide
OL-25866-01
Chapter 18 Configuring VTP
Information About Configuring VTP
Information About Configuring VTP

VTP

A VLAN Trunking Protocol (VTP) is a Layer 2 messaging protocol that maintains VLAN configuration
consistency by managing the addition, deletion, and renaming of VLANs on a network-wide basis. VTP
minimizes misconfigurations and configuration inconsistencies that can cause several problems, su ch as
duplicate VLAN names, incorrect VLAN-type specifications, and security violations.
Before you create VLANs, you must decide whether to use VTP in your network. Using VTP, you can
make configuration changes centrally on one or more switches and have those changes automatically
communicated to all the other switches in the network. Without VTP, you cannot send information about
VLANs to other switches.
VTP is designed to work in an environment where updates are made on a single switch and are sent
through VTP to other switches in the domain. It does not work well in a situation where multiple updates
to the VLAN database occur simultaneously on switches in the same domain, which would result in an
inconsistency in the VLAN database.
The switch supports 1005 VLANs, but the number of configured features affects the usage of the switch
hardware. If the switch is notified by VTP of a new VLAN and the switch is already using the maximum
available hardware resources, it sends a message that there are not enough hardware resources available
and shuts down the VLAN. The output of the show vlan user EXEC command shows the VLAN in a
suspended state.
VTP version 1 and version 2 support only normal-range VLANs (VLAN IDs 1 to 1005). VTP version 3
supports the entire VLAN range (VLANs 1 to 4096). Extended range VLANs (VLANs 1006 to 4096)
are supported only in VTP version 3. You cannot convert from VTP version 3 to VTP version 2 if
extended VLANs are configured in the domain.

VTP Domain

A VTP domain (also called a VLAN management domain) consis ts of one switch or several
interconnected switches under the same administrative responsibility sharing the same VTP domain
name. A switch can be in only one VTP domain. You make global VLAN configuration changes for the
domain.
By default, the switch is in the VTP no-management-domain state until it receives an advertisement for
a domain over a trunk link (a link that carries the traffic of multiple VLANs) or until you configure a
domain name. Until the management domain name is specified or learned, you cannot create or modify
VLANs on a VTP server, and VLAN information is not propagated over the network.
If the switch receives a VTP advertisement over a trunk link, it inherits the management domain name
and the VTP configuration revision number. The switch then ignores advertisements with a different
domain name or an earlier configuration revision number.
When you make a change to the VLAN configuration on a VTP server, the change is propagated to all
switches in the VTP domain. VTP advertisements are sent over all IEEE trunk connections, including
IEEE 802.1Q. VTP dynamically maps VLANs with unique names and internal index associates across
multiple LAN types. Mapping eliminates excessive device administration required fr om network
administrators.