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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter9 Creating and Maintaining VLANs
Using the VLAN Trunking Protocol
The VTP Domain and VTP Modes
A VTP domain (also called a VLAN management domain) consist s of one swi tch or se vera l
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 change s for the
domain by using the command-line interface (CLI), Cluster Management Suite (CMS) software, or
Simple Network Management Protocol (SNMP).
You can configure a supported switch to be in one of the VTP modes listed in Table 9-2 .
By default, the switch is in VTP server mode and in the 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 trunk connections, including
Inter-Switch Link (ISL) and IEEE 802.1Q.
VTP maps VLANs dynamically across multiple LAN types with unique names and internal index
associates. Mapping eliminates excessive device administration required from ne twork adminis trators.
If you configure a switch for VTP transparent mode, yo u can create and modify VLANs, but the changes
are not sent to other switches in the domain, and they affect only the individual switch.
The “Configuring VTP” section on page 9-8 provides tips and c aveat s for c onfig urin g VT P.
Table9-2 VTP Modes
VTP Mode Description
VTP server In this mode, you can create, modify, and delete VLANs and specify other configuration para meters (such
as the VTP version) for the entire VTP domain. VTP servers advert ise their VLAN configurations to other
switches in the same VTP domain and synchronize their VLAN configurations with othe r swi tches ba sed
on advertisements received over trunk links.
In VTP server mode, VLAN configurations are saved in nonvolatile RAM (NVRAM). VTP server is the
default mode.
VTP client A VTP clien t behaves like a VTP server, but you cannot create, change, or delete VLANs on a VTP client.
In VTP client mode, VLAN configurations are not saved in NV RAM .
VTP transparent VTP transparent switches do not participate in VTP. A VTP transparent switch does not adver tise its VLAN
configuration and does not synchronize its VLAN configura tion ba sed on r ece ived a dver tise ment s.
However, in VTP version 2, transparent switches do forward VTP advertisements that they receive from
other switches from their trunk interfaces. You can create, modify, and delete VLANs on a switch in VTP
transparent mode.
In VTP transparent mode, VLAN configurations are saved in NVRAM, but they are not advertised to
other switches.