VLAN questions

Unanswered Question
Apr 17th, 2007

I was wondering how a core switch would feed VLANs to a remote router through other routers. For example, if someone is using DSL on a DSLAM using Vlan 2, which from the DSLAM is connecting to Router A, Router A is then connected via Serial to Router B, which is connected to Router C, then Router D, then to Switch A. Wouldn't Switch A be trunked with router D, which is Trunked using .1q on it's Serial port to Router C's serial, which is trunking with Router B and so on until it gets to Router A, or would it not even need .1q trunking between the routers? Do you have any insight?

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danail-petrov Tue, 04/17/2007 - 13:07

Hi there,

first of all, the dot1q is ethernet tagging mechanism. VLAN stands for "Virtual Local Area Network",so when you have serial HDLC/FrameRelay (they are WAN technologies) or whatever else l2 technology between the routers you can't use vlan tagging there. The trunk port can be only port between switch and first connected router (router A in this case). U can trunk one or more vlans over this connection, but they will exists only between ethernet link (switch <--> router)

Kind Regards,

Danail Petrov


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