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Catalyst 2950 Desktop Switch Software Configuration Guide
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Chapter 15 Configuring VTP
Unders tan ding VTP

The VTP Domain

A VTP do ma in ( also c alle d a VLA N ma nage ment domai n ) con sis ts of o ne sw itch or several
interconnected switches under the same administrative responsibility sharing the same VTP domain
name. A swi tch can be in onl y one V TP dom ain .You make glob al VLA N configu ratio n chang es fo r the
domain by using the command-line interface (CLI), Cluster Management Suite (CMS) software, or
Simple Network Management Protocol (SNMP).
By default, the switch is in 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 o n a VTP server, and VLA N i nfor ma tion is no t pr opagat ed over the network.
If the switch receives a VTP advertisement over a trunk link, it inherits the management domain name
and the V TP configurati on revision number. The switch the n ignores ad vertisem ents wi th a different
domain na m e or an e a rlier c on figuration r evision num be r.
Caution Before addi ng a VTP client switc h to a VTP domain, always verify that its VTP configura tion revision
number i s lower than the configurati on revision number of the other switch es in the VTP dom ain.
Switches in a V TP do ma in a lways us e t he V LAN co nfigurat ion of the swit ch w it h th e high est VTP
configurati on revision nu mb er. If y ou ad d a switc h that ha s a r evision n umb er h ighe r than the r evision
number in the VTP domain, it can erase all VLAN information from the VTP server and VTP domain.
See the “Adding a VTP Client Switch to a VTP Domain” section on page 15-15 for the pr ocedu re for
verifying and resetting th e VTP configurati on revision number.
When you m ake a cha nge t o the V L AN configur ation on a VT P server, the chang e is pr opaga ted to a ll
switch es in the VTP doma in. VTP adv ertisements ar e sent ov er all IEEE 802.1Q t runk connection s. VTP
maps VLANs dy namic ally a cr oss multip le LAN typ es wit h uniqu e names a nd i nternal index associa tes.
Mapping eliminates excessive device administration required from network administrators.
If yo u conf igure a switch f or VTP tran sparen t mode, you can crea te and m odify VL ANs, b ut the changes
are not se nt to other swi tches in the domain, and they affect only the i ndividual switch. However,
configurati on cha nges m a de w hen th e sw itch i s in th is m ode ar e saved in the swi tch runni n g
configurati on and can be saved to the sw itch star tup configurat ion file.
For domain na m e an d p assword configur ation g uide lin es, se e the “VTP Configuration Guidelines”
section on page 15-8.