• Quick question about routers


    Hello Lounge, I was recently trying to sort out a connectivity problem in a small office.

    There are three Windows XP Professional machines in a (wired) workgroup, connected through a router to the WAN. Pretty much like you’d have at home. One morning, two users came into the office first and one (Nikki, the boss) was browsing the internet, and the other (Alex) was doing some stuff locally on her own machine.

    An hour later, the third user (Debbie) came in, started her machine, and couldn’t get on the internet, though Nikki was still on it. Debbie phoned me for help, and I got her on to a Command Prompt and found she had an APIPA address. I got her to do the release/renew thing but she still got an APIPA address. She couldn’t reboot the router as Nikki couldn’t be interrupted, and I didn’t think it would help anyway, as Nikki was using it ok. Alex couldn’t get on the internet either.

    It was early in the morning and I couldn’t get my head round it , so I said I’d call her back. The fact that Nikki was on the internet threw me. A little while later, she called me back and said problem solved, they just restarted everything – all the machines, router, lights, central heating and all. Feminine thinking I know, but it worked.

    So my question is this: can a frozen router keep you connected, provided you’re connected before it freezes? A stalled router was the only thing I could think of, frankly, but maybe there was something I didn’t think of.

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    • #1335451

      Yes, a stalled router is most likely….more specifically the DHCP server within the router.

      If the user has an APIPA address then the router has not completed the DCHP sequence. Attempting to renew and failing demonstrates the issue was DHCP.

      It doesn’t matter that the other PC was working as it would have still been within the DHCP lease time as that will hold it’s IP address until it is either released or renewed, whereupon it would have failed to an APIPA. When the router was rebooted the other machines asked for an IP address via DHCP and were offered new ones.

      If you had configured static IP’s on the machines at the time of the failure, my guess is they would have been able to browse the web. This is because the router was still functioning as a router and could forward http requests over TCP/IP on the bosses PC. Hence by implication DNS was functional, but the APIPA means the DHCP server had fallen over.

    • #1335455

      Aha! Thanks, Tinto, that was my mistake: I thought that if a router froze, then all of it would stop working, not just the DHCP server or anything else in fact. The static address idea is a good tip, too – I’ll remember that.

      Now I can sleep nights.:)

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