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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 9 Creating and Maintaining VLANs
Using the VLAN Trunking Protocol
The VTP Domain and VTP Modes
A VTP domain (also called a VLAN management domain) consists 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 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 network administrators.
If you configure a switch for VTP transparent mode, you 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 caveats for configuring VTP.
Table 9-2
VTP Modes
VTP Mode
Description
VTP server
In this mode, you can create, modify, and delete VLANs and specify other configuration parameters (such
as the VTP version) for the entire VTP domain. VTP servers advertise their VLAN configurations to other
switches in the same VTP domain and synchronize their VLAN configurations with other switches based
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 client 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 NVRAM.
VTP transparent VTP transparent switches do not participate in VTP. A VTP transparent switch does not advertise its VLAN
configuration and does not synchronize its VLAN configuration based on received advertisements.
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.
