Internet connection problem
January 17, 2005 3:37 PM   Subscribe

Internet connection problem. Odd circumstances. Knowledgeable people are invited inside to tell me that I'm missing something obvious.

A friend's computer sits behind a router and receives cable internet. Her computer suddenly stopped being able to connect to the internet at all. She called Comcast, and they blamed malware.

She brought the computer to her boyfriend's house, where I saw it. We hooked it up to his router/cable modem, and indeed it wouldn't connect. I just suggested a clean install (of XP Home) rather than chase down all the problems. She agreed.

The install went well, I installed Firefox and it connected fine. She took the computer home, and it worked great for an hour. Now it won't connect through the router. If she connects directly to her modem, she can access the internet.

I'd be inclined to say that the router's gone bad, except that she had her boyfriend's spare machine at her apartment for a week and it worked fine. And when I first saw it and it wouldn't connect, it was behind a router as well.

Is there some condition that would cause the computer to not function behind a router, assuming that the network settings weren't changed by the users and no additional software had been installed after it was clean? Or should I chalk the other computer's functioning to coincidence and blame the D-link? I don't want to go out to Charlestown to monkey with this thing.
posted by Mayor Curley to Computers & Internet (9 answers total)
I have the same setup and occasionally the same problem. Usually, I perform the following steps:

1) Unplug power to router
2) Unplug power to Cablemodem
3) Count slowly to 15. Open beer.
4) Power up Cablemodem.
5) When lights stabilize on cablemodem, power up router.
6) Drink beer. Wait on lights.
7) When things settle down, I'll access the router through browser and make sure it was able to log in to Comcast.

Usually, 99% of the time, that solves the prob.

Sometimes you just gotta burp it.
posted by TeamBilly at 3:47 PM on January 17, 2005

I would try running the dos command. "winipcfg" Release all. Renew all. That should tell you if the computer is connecting with the router. The router to the modem I would double check the wiring. As for operating systems I would guess that wouldn't do too much to help. FWIW I'm not that computer friendly, but had the same why can't I connect now when I was just yesterday problem. Good luck.

On preview. What billy said.
posted by brent at 3:48 PM on January 17, 2005

There's always the possibility that she's installing some kind of small program that messes up the settings (maybe an applet provided by Comcast?). You overwrote it with XP, she goes back home and after an hour accesses or downloads the program again. You assume she didn't do this; she may not realize she did. My mom is classic for this.
posted by dness2 at 3:59 PM on January 17, 2005

Generally speaking, cable companies have MAC address filtering. The general way to fix it is to do what TeamBilly says: burp it. Sometimes more is required: before step 1 do this:
0a) get on the computer that is working when directly connected to the internet. hook it up to the router like you would normally.
0a) login to your router
0b) click on 'home' up top and 'wan' on the left
0c) you should have 'dynamic ip' selected. near the middle of the page there is a button called 'Clone MAC Address'. click it. then click save.

then follow the steps outlined above by TeamBilly.
posted by escher at 4:26 PM on January 17, 2005

Comcast is evil (but are the only people to offer cable modems in my area). My girlfirend has problems with this as well. However, running Brent's suggestion seems to work just about all the time.
posted by rooftop secrets at 5:44 PM on January 17, 2005

Try a different cable between the modem and computer. The connectors at the ends of the cables are their weak points, and sometimes fail.
posted by Kirth Gerson at 5:54 PM on January 17, 2005

You could try setting the MAC address of her PC to be the same as the one on the router, then connect it directly to the modem. Then change her MAC address back to its default one, and put the router back into the equation, thus tricking the modem into believing the same device was plugged in.

If you don't understand what I'm saying, you may want to disregard this, as you are likely to screw something up trying that.

The cable company can usually also tell you the MAC address and IP address that has been assigned to the device attached to the modem. Make sure it isn't reporting info from the PC, when the router is attached.
posted by stovenator at 10:43 PM on January 17, 2005

what stovenator said, or leave in one configuration (connected directly or through router) for 12 hours, power cycling the modem when you're bored. sometimes companies seem to have strange policies about restricting how often macs change. or that may just be me not understanding things fully.
also, is "winipcfg" the xp version of "ipconfig"?
posted by andrew cooke at 7:06 AM on January 18, 2005

I had the same problem - I found that when I re-formatted my drive and reinstalled a firewall, it was blocking my connection (both the wireless card software and whatever it uses to connect manually through the cable modem).
posted by blackkar at 7:35 AM on January 18, 2005

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