08-29-2007 05:08 AM - edited 03-05-2019 06:10 PM
Can anyone explain what exactly do i achieve with the pruning configuration listed below when there are only specific vlans allowed on the trunk?
interface FastEthernet5/28
switchport access vlan 102
switchport trunk encapsulation dot1q
switchport trunk native vlan 102
switchport trunk allowed vlan 102,120
switchport trunk pruning vlan 2-101,103-119,121-1000
switchport mode trunk
switchport voice vlan 120
speed 100
duplex full
qos trust dscp
Thanks
08-29-2007 05:10 AM
Hi
As far as i can see you don't achieve anything. Pruning is useful to sutomatically stop vlan traffic being propogated down links when that vlan is not in use at the far end of the link but as you have specifically only allowed vlan 102 and 120 traffic then i would say the pruning is unnecessary.
Jon
08-29-2007 05:38 AM
It would help when you have pruning enabled but you do not configure the switchport trunk allowed vlan command under the interface
Narayan
08-29-2007 05:38 AM
Hi,What if a switch and its downstream switches dont have any access ports for vlan 100(for example).in this case pruning avoids unnecessary traffic for vlan100 over the trunks.
08-29-2007 05:40 AM
You are right but when we allowe only specific vlans over the trunk using the switchport trunk allowed vlan command, pruning would be unnecessary.
Even if do not prune for eg vlan 200, it will not be allowed over thetrunks due to the above command
HTH
Narayan
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