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New Member

vlan tag/pruning?

We are a wholesale provider to an ISP,we are suppling them vlan-140 on our backbone. They are tied into a 4006 switch and are dropped off at our 6509. The ISP wants to use vlan tagging to seperate out his equiptment for security.

Our question is do we have to do anything to match his vlan's, or are we just a conduit (generic carrier) for him and don't care what he does with vlan's.

New Member

Re: vlan tag/pruning?


VLAN tags are applied to packets that traverse trunked links. As a packet leaves a trunked port, the packet is forwarded to the assigned VLAN and the tagging is stripped. The tags are then not re-applied until the packet leaves via another trunked port. So, if he directs his packets to you on a link that has only one vlan assigned, then there is no tag. When you pick his packet up on VLAN 140 via a trunked configuration, a tag for VLAN 140 is applied to the packet. This is different, however, if you are using some kind of tunneling mechanism. Let me know if this helps or if you need more information.



Re: vlan tag/pruning?

Port which are not trunk, doesn;t tag vlan. So if they move their vlan to 140 and on your side it is vlan 1 then that would work unless they don;t enable trunk.

Hope this helps..


Re: vlan tag/pruning?

Thanks I think we are on the right path. We are not trunking our port we are set

as a straight vlan 140 on our side. The customer wants to use vlans 10,11,12

on his network. I think we are generic to him with this configuration are we

correct ? We don't really care what he is doing on his end as far as trunking,

is that correct?

New Member

Re: vlan tag/pruning?

e- Your customer can use whatever vlans he wants at his site, just be sure that he is not trying to connect to you with a trunk. If he does, I believe that the traffic may pass through, but you will get many errors from your equipment stating "port x/x receiving dot1q/isl packets on a non-trunk port"


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