How to set up a wireless router to work with a DSL modem

Not so much a guide as a subtle problem I had.

Was trying to get wireless router to work at a friend's apartment and nothing I did with the router would get it to connect to the modem, which ran an ADSL line on PPPoE. Eventually I noticed that it was getting an internal IP (192.168.1.100) assigned to it, meaning something else was acting as a DHCP server. A-Ha! Take on Me! Logging on to the modem (a "HuaWei MT800A"), I set the DHCP server to "none" and (this is key) went to the "save" menu and hit "save". Log back on to the router and choose PPPoE and set the logon/password fields and Viola da Gamba, it works!