meaning of modem lights

[Thufir]

I have a cable ISP and a bog standard cable box.  Not often, perhaps ever 
six months or even less frequently, I'll have connection problems.  I'm 
at a bit of a loss as to how to troubleshoot them.

The modem lights are all solid, the activity light is blinking as it 
normally does, as does the ethernet jack on the box.  Running "ifconfig 
eth0 down," and then bringing it backs up fails to acquire a useful IP 
address.

It's so infrequent that I really doubt it could be the cable or other 
hardware problem.  When I contact the ISP they say "no connection 
problems in your area," but I just don't believe them.

What can I do in a situation like this?  I resorted to booting to a live 
disc, same result, which implies to that it's not my system, and I've, to 
my mind at least, ruled out hardware problems.

Do those blinking lights on the modem *really* mean that the modem has an 
internet connection, or just a connection to the ISP?

I know on windows it's sometimes necessary to "rebuild" the networking, 
but, as the live cd gives the same result, and the situation always 
resolves itself overnight, that doesn't seem to be the problem here.



thanks,

Thufir