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Catalyst 2950 Desktop Switch Software Configuration Guide
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Chapter 15 Configuring VTP Understanding VTP

VTP Modes

You can co nfigure a supporte d switch t o be in one of the VTP mod es listed in Table 15-1.
When the network is configured with more than the maximum 250 VLANs, the switch automatically
changes from VTP server or client mode to VTP transparent mode. The switch then operates with the
VLAN configuration that preceded the one that sent it into transparent mode.

VTP Advertisements

Each switch in the VTP domain sends periodic global configuration advertisements from each trunk port
to a rese rved multicast address. Neighboring switches receive these advertisements and update their VTP
and VL AN configur ation s a s nece ssa ry.
Note Be cause tr unk port s se nd an d r ece ive VT P adverti se ment s, you mu st ensur e that at le as t one tr unk por t
is configured on the switch an d that th is trunk por t is conne cted to the trunk port of a second sw itch.
Otherwise, the switch cannot receive any VTP advertisements. For more information on trunk ports, see
the “Confi guri ng V LAN Trunks” section on pa ge 14-1 5.
VTP advertisements distribute this global domain information:
•VTP domain na me
•VTP configurati on revision number
•Update identity and update timestamp
Table 15-1 VTP Mode s
VTP Mode Description
VTP server In VTP server mode, you can create, modify , and delete VLANs and specify other configuration parameters
(such as the VTP v er sion) for the entire VT P domain. VT P serv ers ad vert ise their VL AN conf ig uratio ns to
other s wit che s in the same VT P doma in a nd sync hro nize thei r V LAN c on figurations with othe r swit ches
based on advertiseme nts rece ived over trunk links.
In VTP server mode, VLAN configurations ar e saved in nonvolatile RAM (NVRAM). VTP server is the
default m ode.
VTP client A VTP client behaves like a VTP ser ver, but you cannot create, change, or delete VLAN s on a VTP client.
In VTP clien t mode, V LAN configurat ions are not saved in NVRAM.
VTP transparent VTP transparent switches do not participate in VTP. A VTP transparent switch does not adv ertise its VLAN
configurat ion an d d oes n ot sync hro nize i ts VL AN c onfigura tio n base d on re ceived advertise ment s.
However, in VTP ve rsion 2, transparent switch es do forward VTP advertisements that they receive from
othe r switches from their trunk interfaces. You can create, modi fy, and delete VLANs on a switch in VTP
transparent mode. The switch must be in VTP transparent mode when you create extended-range VLANs.
See the “Configuring Exte nded- Ra nge V LA Ns” secti on on page 14-1 2.
When the switch is in VTP transparent mode, the VTP and VLAN configurations are saved in NVRAM,
but they are not advertised to other switches. In this mode, VTP mode and doma in name are saved in the
switch running configuration and you can save this information in the switch startup configuration file by
entering the copy running-config startup-config privileged EX EC com ma nd .