vtp pruning ,help

Answered Question
May 13th, 2010
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VTP pruning is not designed to function in VTP transparent mode. If one or more switches in the
network are in VTP transparent mode, you should do one of these:
1.  Turn off VTP pruning in the entire network.
2.  Turn off VTP pruning by making all VLANs on the trunk of the switch upstream to the VTP transparent switch pruning ineligible.

why does the second turn off vtp pruning on vlans that upstream to the vtp transparent ? if not do so, what will happen? please give me a example,thanks

Correct Answer by Ganesh Hariharan about 6 years 11 months ago


VTP pruning is not designed to function in VTP transparent mode. If one or more switches in the
network are in VTP transparent mode, you should do one of these:
1.  Turn off VTP pruning in the entire network.
2.  Turn off VTP pruning by making all VLANs on the trunk of the switch upstream to the VTP transparent switch pruning ineligible.

why does the second turn off vtp pruning on vlans that upstream to the vtp transparent ? if not do so, what will happen? please give me a example,thanks

Yes you are right VTP pruning  has no effect on switches in the VTP transparent mode. Instead, those switches must be configured manually to “prune” VLANs from trunk links.


For your query pruning is always configured on the upstream side of a trunk. (The downstream side switch doesn’t have any ports that belong to the pruned VLAN, so there is no need to prune from that end). This is the reason for second query ..


Hope to Help !!


Ganesh.H


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hblfzhangzhiwei Thu, 05/13/2010 - 02:26
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because transparent mode do not support vtp pruning , so when vlan on transparent mode switch is not same with vlan on the downsteam vtp pruning switch, it can cause network problem.

exaple :

1----2-----3

one is vtp server , two is vtp transparent , three is client .

one has vlan 1.2.3 , enable vtp pruning , two has vlan 2,3 , three has vlan 3, the vtp server ,one, will prune vlan 2,so that the vlan 2 on two can not communicate with others.

Correct Answer
Ganesh Hariharan Fri, 05/14/2010 - 10:27
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VTP pruning is not designed to function in VTP transparent mode. If one or more switches in the
network are in VTP transparent mode, you should do one of these:
1.  Turn off VTP pruning in the entire network.
2.  Turn off VTP pruning by making all VLANs on the trunk of the switch upstream to the VTP transparent switch pruning ineligible.

why does the second turn off vtp pruning on vlans that upstream to the vtp transparent ? if not do so, what will happen? please give me a example,thanks

Yes you are right VTP pruning  has no effect on switches in the VTP transparent mode. Instead, those switches must be configured manually to “prune” VLANs from trunk links.


For your query pruning is always configured on the upstream side of a trunk. (The downstream side switch doesn’t have any ports that belong to the pruned VLAN, so there is no need to prune from that end). This is the reason for second query ..


Hope to Help !!


Ganesh.H


Remember to rate the helpful post

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