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jfmezei
Premium Member
join:2007-01-03
Pointe-Claire, QC

jfmezei

Premium Member

Adding information to PPPoE packets

OK, I know that the Bell BAS router gets the DSLAM port number for a PPPoE session. Not sure if this is just for the PPPoE session establishement phase or if for every packet.

How/where is this information added to the packet ? Is this something added to the ethernet header ? PPPoE header ? Tagged to the end of the packet ?

And more importantly, would it be easy/possible for the BAS to forward that info to the ISP ?
freejazz_RdJ
join:2009-03-10

freejazz_RdJ

Member

The association of a physical port to a session with PPPoE probably doesn't come from a string received by the BRAS. That is to say that neither the client nor an intermediate device sends a port ID usually, just MACs, although he BRAS/LAC also sends its host name.

What is far more likely is that there is a 1:1 vlan:port setup. So the BRAS knows that on Eth0, VLAN 1-1 is Shelf/Slot/Port 1 of Dslam1 MezeiVille CO. There are ways to send information on the originating DSL port to the LNS, perhaps using radius attribute 87, NAS-Port-ID. It resembles DHCP option 82 in that way except the source port ID isn't inserted by the originating switch.