Bizarre failure modes- A cable modem story
Edit: Scratch all of my dumb convoluted theories kids. Turns out, and I told him to check on this a month ago, they shut his account down due to copyright infringement, specifically downloading old episodes of Heroes. The best part is that only one technician, out of something like 6, actually bothered looking at his account and finding the issue.
Sometimes a device will fail in a way that is, to put it gently, retarded. Radiator thermostats stick closed, a dhcp device will issue an immediate expiration of leases just as it dies, a sensor will report that everything is just fine, and all that sort of thing.
This is about a cable modem.
The person who has tolerated me the longest, my friend Art, has been having internet issues. Specifically he can’t connect to it. He would get issued an address in a 172 range, which is a private subnet, which is a problem since he connects directly to a cable modem and should be receiving a publicly routed real boy ip address. In Windows it would also be assigned a gateway in the 172 range.
Did I mention he lives several states away, so I had to handle this all by phone? Yeah, good times.
So we plunk away at it, do a repair install, try a different NIC, and so on. I remember he has a router so I walk him through setting it up, but I’m pretty sure he goofed and plugged the cable modem into one of the 4 internal ports, a fact that would set my diagnosis back a ways.
Cox said everything looks fine (a foul lie), and said he should power off his modem for 10 minutes and try again. Try not to fall for this people, make them wait it out with you if they insist on such a time. There’s no real difference between 10 seconds and 10 minutes, aside from some heat maybe.
He doesn’t have another computer and knows only technophobes apparently, so trying another computer is out of the question. So I convince him to download Ubuntu and burn a livecd of that. We boot up and…. a 172 address greets us. We look in resolv.conf, however, and guess what? There’s Cox information in there. A 24. gateway and a Cox search domain.
So we hook the router up again, double checking the connections this time, and lo, he has a real (local) ip and can hit the router’s configuration page. Meanwhile it’s acquired the same bogus info he was getting, so here’s my theory.
The modem broke, and can no longer obtain an ip, but is set to do some weird fallback behavior and is assigning an ip based on that, plus a default gateway that it’s set to search for initially, or something very much like that.
He’s currently out getting another modem, so we shall see.