The manual that came w/ my DSL modem (which has an Alcatel chipset) gave no refrences to it having any IP capabilities at all: just have your PC speak PPPoE and the modem will handle the rest. After spending enough time on the phone w/ tech support they admited to me that the modem does in fact have an IP address. My modem's default IP was 10.0.0.1/24. After configuring my ethernet interface connected to the modem to have an address on that network I was able to ping the modem, telnet into the modem to view/change configuration information, and use SNMP to poll stats the modem.

When my modem fails it generally goes to a "dsl-down ethernet-down" condition that I can detect by pinging the modem (if the modem is up and the internet is down, I can detect that by SNMP poling the modem and/or pinging the "internet").

Poke around and you'll probably find out that your modem does actually have an IP support and an IP address that you can ping. The manufacturer is probably just hiding this from you.