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Difference between prunning & allowing vlan

Hi I would like to clarify what is the difference between the effect that cause the command prunning and the effect that cause the command allowe.

Example:

If I put on my trunk inerface the command

swichport trunk allowed vlan 2,56

or

swichport trunk pruning vlan except 1,2,56,1002-1005

what is the difference between both?wich one is better to improve the performance of a switch?

Note: I have a vtp domain with 30 vlans

thanks

lp

3 REPLIES

Re: Difference between prunning & allowing vlan

On devices that do not support VTP pruning, you must manually configure the VLANs allowed on trunks. Please also check the following URL for an explanation of pruning:

http://www.cisco.com/en/US/products/hw/switches/ps663/products_configuration_guide_chapter09186a00800e47e3.html#10027

Regards,

Leo

Cisco Employee

Re: Difference between prunning & allowing vlan

VTP Pruning does not remove STP from Trunks while clearing VLANs off the trunk manually removes it. Its a good idea to clear the trunks manually.

New Member

Re: Difference between prunning & allowing vlan

Pruning a vlan is used to avoid uselees flooding of this vlan (broadcast, multicast, unknown unicast) to be sent on trunks connected to switches where this vlan is not used (no connected port in the vlan).

Removing a vlan from a trunk prevents the use of this vlan on the switch behind this trunk. If you configure a port in this vlan, it won't be able to communicate with others devices of the vlan on other switches.

HTH,

Christophe

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