Enabling Vtp Pruning - Cisco Catalyst 2000 Configuration Handbook

in that you can create, delete, or modify VLANs in the local VLAN database. The differ-
ence is that these changes are not propagated to other switches. In addition, the local
VLAN database does not accept modifications from other switches. VTP transparent
mode switches forward or relay information between other server or client switches. A
VTP transparent mode switch does not require a VTP domain name.
Note The global configuration command vtp mode is not supported on all switches that
run the IOS.

Enabling VTP Pruning

By default all the VLANs that exist on a switch are active on a trunk link. As noted in
section "6-3: Trunking," you can manually remove VLANs from a trunk link and then add
them later. VTP pruning allows the switch to not forward user traffic for VLANs that are
not active on a remote switch. This feature dynamically prunes unneeded traffic across
trunk links. If the VLAN traffic is needed at a later date, VTP dynamically adds the
VLAN back to the trunk.
Note Dynamic pruning removes only unneeded user traffic from the link. It does not pre-
vent any management frames such as STP from crossing the link.
(Optional) Enable VTP pruning.
1.
a. Enable pruning:
(privileged) vlan database
(vlan_database) vtp pruning
After VTP pruning is enabled on one VTP server in the domain, all other switch-
es in that domain also enable VTP pruning. VTP pruning can only be enabled on
switches that are VTP version 2-capable, so all switches in the domain must be
version 2-capable before you enable pruning.
Note The switch must be VTP version 2-capable but does not need to have version 2
enabled to turn on pruning.
b. (Optional) Specify VLANs that are eligible for pruning:
(global) interface type mod/port
(interface) switchport trunk pruning vlan remove vlanlist
By default all the VLANs on the trunk are eligible for pruning. You can remove
VLANs from the list of eligible VLANs using these commands. After a VLAN
has been removed from the eligible list, it cannot be pruned by VTP. To add the
Chapter 6: VLANs and Trunking 101