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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
Two configurations can cause a switch to automatically change its VTP mode:
•
When the network is configured with more than the maximum 250 VLANs
(some models support a maximum of 64 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.
•
When a multi-VLAN port is configured on a supported switch in VTP server
mode or client mode, the switch automatically changes to transparent mode.
The
“VTP Configuration Guidelines” section on page 8-18
provides tips and
caveats for configuring VTP.
VTP Advertisements
Each switch in the VTP domain sends periodic global configuration
advertisements from each trunk port to a reserved multicast address. Neighboring
switches receive these advertisements and update their VTP and VLAN
configurations as necessary.
Note
Because trunk ports send and receive VTP advertisements, you must ensure
that at least one trunk port is configured on the switch and that this trunk port
is connected to the trunk port of a second switch. Otherwise, the switch cannot
receive any VTP advertisements.
VTP advertisements distribute the following global domain information in VTP
advertisements:
•
VTP domain name
•
VTP configuration revision number
•
Update identity and update timestamp
•
MD5 digest