what happens when vlan pruning is none

Unanswered Question


I just curious if I were to put in the following statement:

interface GigabitEthernet0/27

switchport trunk encapsulation dot1q

switchport trunk pruning vlan none

switchport mode trunk

What will happen to the switch interface? Does it mean that no other VLANs are carried forward from this interface except VLANs that are created within the switch?

Any advise?

Thanks in advance.

I have this problem too.
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Jon Marshall Wed, 05/28/2008 - 14:45

Not really sure what you are asking here. If you have "switchport trunk pruning vlan none" then you are saying do not prune any vlans from the trunk link. So the vlans could be created on that switch or they could be created on another switch as Andrew says.

On this switch all it says is that any traffic for any vlan that is allowed on the trunk will be forwarded on that interface regardless of whether any ports further down the line are in that vlan.


Kevin Dorrell Thu, 05/29/2008 - 23:20

Not really. The switch would still have to know about the VLAN.

If you have VTP pruning enabled, VTP will automatically prune a VLAN off a trunk if there are no downstream clients for the VLAN.

All the command does is to disable that feature for this trunk. It means is that VTP would not automatically prune the VLAN from the trunk.

If the switch knows about the VLAN, and if the VLAN has not been manually disallowed on the trunk, then the trunk would forward the VLAN, even if there are no downstream clients for the VLAN.

Kevin Dorrell



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