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Cisco IE 2000 Switch Software Configuration Guide
OL-25866-01
Chapter 18 Configuring VTP
Information About Configuring VTP
Note For VTP version 1 and 2, before you create extended-range VLANs (VLAN IDs 1006 to 4096),
you must set VTP mode to transparent by using the vtp mode transparent global configuration
command. Save this configuration to the startup configuration so that the switch starts in VTP
transparent mode. Otherwise, you lose the extended-range VLAN configuration if the switch
resets and boots up in VTP server mode (the default).
VTP version 3 supports extended-range VLANs. If extended VLANs are configured, you cannot
convert from VTP version 3 to VTP version 2.
If you configure the switch for VTP client mode, the switch does not create the VLAN database file
(vlan.dat). If the switch is then powered off, it resets the VTP configuration to the default. To keep
the VTP configuration with VTP client mode after the switch restarts, you must first configure the
VTP domain name before the VTP mode.
When a switch is in VTP server mode, you can change the VLAN configuration and have it
propagated throughout the network.
When a switch is in VTP client mode, you cannot change its VLAN configuration. The client switch
receives VTP updates from a VTP server in the VTP domain and then modifies its configuration
accordingly.
When you configure the switch for VTP transparent mode, VTP is disabled on the switch. The
switch does not send VTP updates and does not act on VTP updates r eceived from other switches.
However, a VTP transparent switch running VTP version 2 does forward received VTP
advertisements on its trunk links.
VTP off mode is the same as VTP transparent mode except that VTP advertisements are not
forwarded.
Caution If all switches are operating in VTP client mode, do not configure a VTP domain name. If you do, it is
impossible to make changes to the VLAN configuration of that dom ain. Therefore, make sure you
configure at least one switch as a VTP server.
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.
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