Dew to the limitations of my TP-Link MR3220 (it only handles 16 elements in the access control list) I'm looking into adding pppoe link into one of my ARM devices.
I've not yet chosen which one although the NAS, that is on all the time (GoFlex Net <GFN> running Slackware ARM 14.1), seems a natural candidate but it only has 1 usable NIC (the other port in the kirkwood SOC on the GFN is not wired): is it possible to use that one NIC to do both my LAN traffic and handle the WAN pppoe connection ? maybe by configuring an alias for the LAN traffic ?

I use PPPoE on Linux and I have a dedicated interface which is plugged into the FTTC (the name we use for Fibre broadband in the UK) modem. I hadn't ever thought of plugging the modem into a switch and seeing if I could still run PPPoE over it. I don't know much about Ethernet but I can't really see how it could work. I'd be curious to know whether it does though!

I`m in vacation right now but I`ll look into it when i`m back. I`m not into any detail about pppoe but I`m assuming it can`t operate any lower than mac? so the switch itself should not be an issue ... but that can be tested really easily.
Is rp-pppoe the right software approach ?

Ooops: I reviewed iso osi and Ethernet stacks. I forgot that switches operate between levels 2 and 3 (some even claim that they operate @ level 2.5). Apparently also pppoe is stuck in the realm between 2 and 3. I`m beginng to think that there`s a good chance that Stuart is darn right.

Ok I'm back home ... and one of the first things I got round to doing is wiring up a small 5 port 10/100 switch between my TP-Link router and the pppoe device (in my case it's a wireless link antenna that speaks something like hyperlan2 with my ISP and pppoe on my side). I'm currently editing this message with the switch wired up.
I even rebooted the router to make sure that the connection is reinitiated correctly.
I've been thinking on what I want to do and even if it was possible it would not be a good idea:
possibly everyone from the LAN could start initiating pppoe connections and possibly sniff credentials too.
I got fast ethernet usb dongles from ebay at about 3 euro each (including shipping) ... I'll plug one of those in the GoFlexNet to handle the pppoe connection keeping the Ethernet port for the LAN traffic.
If firewalling and pppoe prove to be too cpu intensive I'll move to a dedicated dockstar or something else.