[c-nsp] NAS-Port = 0 with PPPoE relay from 1811 to 7200

[Andrew Jones]

Hi Guys,
I'm having some trouble with my PPPoE relay setup. I have 1811s relaying to a
7204-g1 which terminates the l2tp tunnels using vpdn multihop. Authentication is
via radius, and done my the 7200 only. The problem is that any PPPoE sessions
which come in on a dot1q subint are reported in the radius accounting log as
being NAS-Port = 0. The system works fine if the PPPoE session terminates on a
normal interface or a vlan interface.

I've tried using "radius-server attribute nas-port format d" on both the 1811
and the 7200, but it hasn't fixed the issue, I expect because the 1811 is not
actually using radius, it's all done by the 7200.

Any ideas on how to get a proper NAS-Port value?

Thanks,
Andrew