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Community Member

I have a VLAN and Trunk question

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.

Thanks,

Brent

1 ACCEPTED SOLUTION

Accepted Solutions

Re: I have a VLAN and Trunk question

Hi,

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

http://www.cisco.com/en/US/docs/switches/lan/catalyst2900xl_3500xl/releasesa4/eesoftconfig/masctrnk.html

Hope this helps out your query !!

Regards

Ganesh.H

3 REPLIES

Re: I have a VLAN and Trunk question

Hi,

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

http://www.cisco.com/en/US/docs/switches/lan/catalyst2900xl_3500xl/releasesa4/eesoftconfig/masctrnk.html

Hope this helps out your query !!

Regards

Ganesh.H

Community Member

Re: I have a VLAN and Trunk question

Thanks dude..

that's awesome!

Re: I have a VLAN and Trunk question

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..

http://www.cisco.com/en/US/products/hw/switches/ps663/products_tech_note09186a0080094713.shtml

Hope this helps.. all the best...

Raj

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