Sunday, July 25, 2010

VTP Pruning

VTP Pruning is a feature that can be enabled when the switch is in the Server mode and will be applied to all switches in the same domain if VTP pruning is enabled on one server. The command for VTP pruning is “#vtp pruning” on the switch’s configuration mode. This feature can filter and block unnecessary information.

Take for example switch A that has VLAN 2-20 enabled on it, and switch B that has VLAN 15-25 enabled on it. Without VTP pruning, advertisements are being broadcasted from switch A to B and backwards for all the VLANS. This will result in useless traffic being sent, since switch B does not have VLAN 2-14 on it and does not need this “waste” of information/traffic. Switch B needs only information for VLAN 15-20. The same goes for switch A that receives broadcasts for VLAN 15-25, while it needs only information for VLAN 15-20.

By using VTP pruning, the problem above can be avoided. The receiving switch will automatically detect and prune unnecessary VLAN information (traffic) so that only usable information will be forwarded.

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