Chapter 8      Configuring VLANs
Using VTP
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Catalyst 2900 Series XL and Catalyst 3500 Series XL Software Configuration Guide
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VTP Configuration Guidelines
The following 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.