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Catalyst 2960 and 2960-S Switch Software Configuration Guide
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Chapter 14 Configuring VTP
Understanding 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 stack and that this trunk port is connected to the trun k port of another switch.
Otherwise, the switch cannot receive any VTP advertisements. For more information on trunk po rts, see
the “Configuring VLAN Trunks” section on page 13-13.
VTP advertisements distribute this global domain information:
• VTP domain name
• VTP configuration revision number
• Update identity and update timestamp
• MD5 digest VLAN configuration, including maximum transmission unit (MTU) size for each
VLAN.
• Frame format
VTP advertisements distribute this VLAN information for each configured VLAN:
• VLAN IDs (IEEE 802.1Q)
• VLAN name
• VLAN type
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 or version 3, transparent switches do forward VTP advertisements that they
receive from other switches through their trunk interfaces. You can create, modify, and delete VLANs on
a switch in VTP transparent mode.
In VTP versions 1 and 2, the switch must be in VTP transparent mode when you create extended-range
VLANs. VTP version 3 also supports creating extended-range VLAN s in client or server mode. See the
“Configuring Extended-Range VLANs” section on page 13-10.
When the switch is in VTP transparent mode, the VTP and VLAN configurations are saved in NVRAM,
but they are not advertised to other switches. In this mode, VTP mode and domain name are saved in the
switch running configuration, and you can save this information in the switch start up configuration file by
using the copy running-config startup-config privileged EXEC command. The running configuration and
the saved configuration are the same for all switches in a stack.
VTP off A switch in VTP off mode functions in the same manner as a VTP transparent switch, except that it does
not forward VTP advertisements on trunks.
Table 14-1 VTP Modes (continued)
VTP Mode Description