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Catalyst 2900 Series XL and Catalyst 3500 Series XL Software Configuration Guide
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Chapter 8 Configuring VLANs
Using VTP
VTP Configuration Guidelines
These sections describe the guidelines you should follow when configuring the VTP domain name and
password and the VTP version number.
Domain Names
When configuring VTP for the first time, you must always assign a domain name. All switches in the
VTP domain must also be configured with the same domain name. Switches in VTP transparent mode
do not exchange VTP messages with other switches, and you do not need to configure a VTP domain
name for them.
Caution Do not configure a VTP domain if all switches are operating in VTP client mode. If you configure
the domain, it is impossible to make changes to the VLAN configuration of that domain. Therefore,
make sure you configure at least one switch in the VTP domain for VTP server mode.
Passwords
You can configure a password for the VTP domain, but it is not required. All domain switches must share
the same password. Switches without a password or with the wrong password reject VTP
advertisements.
Caution The domain does not function properly if you do not assign the same password to each switch in the
domain.
If you configure a VTP password for a domain, a Catalyst 2900 XL or Catalyst 3500 XL switch that is
booted without a VTP configuration does not accept VTP advertisements until you configure it with the
correct password. After the configuration, the switch accepts the next VTP advertisement that uses the
same password and domain name in the advertisement.
If you are adding a new switch to an existing network that has VTP capability, the new switch learns the
domain name only after the applicable password has been configured on the switch.
Upgrading from Previous Software Releases
When you upgrade from a software version that supports VLANs but does not support VTP, such as
Cisco IOS Release 11.2(8)SA3, to a version that does support VTP, ports that belong to a VLAN retain
their VLAN membership, and VTP enters transparent mode. The domain name becomes UPGRADE,
and VTP does not propagate the VLAN configuration to other switches.
If you want the switch to propagate VLAN configuration information to other switches and to learn the
VLANs enabled on the network, you must configure the switch with the correct domain name, the
domain password, and change the VTP mode to VTP server.
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