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16-3
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-21521-01
Chapter 16 Configuring VTP
Understanding VTP
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. However,
configuration changes made when the switch is in this mode are saved in the switch running
configuration and can be saved to the switch startup configuration file.
For domain name and password configuration guidelines, see the “Dom
ain Names” section on
page 16-9.
VTP Modes
You can configure a supported switch or switch stack to be in one of the VTP modes listed in Table 16-1.
Ta ble 16-1 VTP Modes
VTP Mode Description
VTP server In VTP server mode, you can create, modify, and delete VLANs, and specify other configuration
parameters (such as the VTP v
ersion) 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.
VTP server is the default mode.
In VTP server mode, VLAN configurations are saved in
NVRAM. If the switch detects a failure while
writing a configuration to NVRAM, VTP mode automatically changes from server mode to client mode. If
this happens, the switch cannot be returned to VTP server mode until the NVRAM is functioning.
VTP client A VTP client behaves like a VTP server and transmits and
receives VTP updates on its trunks, but you
cannot create, change, or delete VLANs on a VTP client. VLANs are configured on another switch in the
domain that is in server mode.
In VTP versions 1 and 2, in VTP client mode, VLAN configurations are not saved in NVRAM. In VTP
v
ersion 3, VLAN configurations are saved in NVRAM in client mode.
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
VLA
Ns. VTP version 3 also supports creating extended-range VLANs in client or server mode. See the
“Configuring Extended-Range VLANs” section on page 15-10.
In VTP versions 1 and 2, the switch must be in VTP tra
nsparent mode when you create private VLANs and
when they are configured, you should not change the VTP mode from transparent to client or server mode.
VTP version 3 also supports private VLANs in client and server modes. See Chapter 18, “Configuring
Private VLANs.” When private VLANs are configured, do not ch
ange the VTP mode from transparent to
client or server mode.
When the switch is in VTP transparent mode, the VTP a
nd 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
swit
ch running configuration, and you can save this information in the switch startup configuration file by
using the copy running-config startup-config privileged EXEC command. In a switch stack, 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.