I have a VLAN and Trunk question

Answered Question
Dec 15th, 2009

Is there a way to configure a trunk so that only certain vlan tags are allowed through. I'm pretty sure there is I'm just wondering if someone can point me to a doc of some kind .. or shoot me down.



I have this problem too.
0 votes
Correct Answer by Ganesh Hariharan about 6 years 10 months ago


Yes you can configure a trunk and allow only certain vlans check out the below link how to configure :-


Hope this helps out your query !!



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Overall Rating: 5 (1 ratings)
sachinraja Tue, 12/15/2009 - 09:13

Hi Brent

Ganesh is right on the configuration on allowing certain vlans to go on a trunk.. but as a best practice you can do the following to avoid unncessary broadcasts of vlan information across layer 2 trunks:

1) have your switches with vtp mode transparent configured.. doing this, you can make sure you only have vlans necessary on the edge switch to be defined on the trunk.. this can also avoid configuration register issues you can face with server/client mode.. but it depends on what your network size is, and how efficiently you can manage your vlan configurations..

2) dont have your vlan 1 as native vlans on your trunks.. if possible shutdown vlan 1 on all switches, and have a seperate management vlan.. CDP, VTP, PaGP packets are forwarded by default over VLAN 1.. you can have vlan hopping attacks etc due to this..

there are many more standard practices given in this doc which can help you..


Hope this helps.. all the best...



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