The way to tell this is to swap the modem out.

by R. Proffitt Moderator - 8/3/12 1:23 PM

In Reply to: Problem with Motorola 3347 modem by KenColorado

As to buying a new one, I gifted two out on freecycle since I moved off DSL years ago. Be sure to check into freecycle.org and the free areas of craigslist as there are a lot of DSL modems in closets.

Most ISPs supply the modem+router so why not use theirs?
Bob