According to Brian Doob:
I just moved to an apartment where I'll be getting MTS ADSL (Shaw High Speed is not available). How do I set up Linux to use it? I know you need to use PPPoE, but I don't know how to do that. I have heard that you need to make other adjustments to take proper advantage of it. I'm getting "Starter DSL" (to start with), but I don't think that makes a difference. I'm currently running both Red Hat 7.2 and Gentoo 1.1a. How do I set things up? Thanks.
A quick Google search for redhat, adsl, and pppoe came up with several hits, some more useful than others (as usual). Among the most useful (at least as far as I browsed) was this one...
Configuring a Secure Linux® ADSL PPPoE Connection http://www.skaht.com/linux/adsl/
It tends to focus particularly on the security aspects, but does give some background on PPPoE setup, including some nice diagrams and some advice on startup script setup. It doesn't focus on Red Hat 7.2 specifically, so there may actually be a simpler way of setting things up in a way that's consistent with the Red Hat way of doing things.