Well, out of curiosity I unplugged my phone line from my DSL modem, and 
let it retrain and no problems. I even turned off my DSL modem and 
turned it back on, and m0n0wall reconnected transparently without me 
even knowing. Next, I tried leaving my modem plugged in, but unplugging 
the phone line for an extended period of time until m0n0wall reported a 
LINK DOWN event in the log. Then I plugged it back in and immediately it 
re-established my connection.

Now, the interesting thing is that even with keep-alive set to 0 to 
theoretically disable LCP echo requests, I still see "mpd: [pppoe] LCP: 
no reply to 1 echo request(s)" and so on when the phone line is 
disconnected. Why is this?