[RP-PPPoE] Multiple PPPoE sessions over 1 ethernet port

[Dave]

Hello Everyone,

I have run multiple pppoe sessions on 1 server for a years without 
issue, but each is either on a different physical NIC (different modems) 
or there are 2 sessions to the same BRAS/DSLAM (whatever), so same modem.

I'm now faced with a new issue.  2 ISPs, 2 Modems, but 1 Ethernet Port.  
Is this possible?

How does rp-pppoe know which session to maintain over which modem (does 
it even, can this even be done)?

I'm likely going to try it next week unless someone has a good reason 
for me not to, any pointers would be very welcome too!

Dave