Some time ago now I was fortunate enough acquire a ZyXEL VES1724-55C VDSL DSLAM.
I had a quick play with it, and then loaned it to someone that also had a hankering to play with a DSLAM. They did a great job of documenting their findings on their blog, alexhorner.cc
One of my aspirations was to replicate a UK style wholesale internet provider similar to Openreach. In this model, DSL users send PPPoE, which is terminated on a LAC (L2TP Access Concentrator) operated by the wholesaler. The LAC then does a look up based on the domain in the users username (usually via RADIUS) and then tunnels the PPP via L2TP to the ISPs LNS (L2TP Network Server) where the ISP can terminate the PPP and provide one of their IP addresses.
Or at least that's how it used to work - I'm not sure how things have since evolved with FTTP etc, with other words like BRAS and BNG being thrown into the mix, so assume this information is out-of-date.
Forewarning: This isn't meant to be a complete step-by-step guide, just some clues to get you started. Sorry to disappoint!
