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DHCP not working?


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#1 BenGalaxy

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Posted 15 November 2010 - 12:31 AM

Equipment: Linksys WRT54G2 router, Arris TM602G cable modem + Ambit U10CO18
OS: Windows 7 Home Premium 64-bit
ISP: Cox Communications

Ever since I moved I've had nothing but trouble keeping a connection with my modem/router. We just moved down the street and have the same ISP as before, but something is going wonky at this house.

The issue seems to be that DHCP just simply isn't working. Within 1-2 hours of powercycling all my network equipment I lose the ability to access my router's configuration page. In addition, every time I start my computer up it takes at least a minute before I'm able to access the Internet; my systray shows that my computer is trying to identify its network during that time. ipconfig /release and /renew doesn't work. It gets hung up on renewing and then gives me the error 'Unable to contact DHCP server.' I've cloned my PC's MAC address which had no results. Plugging the ethernet cable into a different port doesn't work (and besides, the problem affects wireless as well). I've tried two separate modems and gotten the same results. My router's firmware is up-to-date, and it's configuration settings are all correct--or at least the same as they were in the old place when it worked perfectly.

Bypassing the router and plugging straight into the modem works just fine. So obviously the problem has to do with the router, but I don't think it's my hardware that's failing, as everything worked perfectly in our last house--unless by some amazing coincidence my router went bad on the exact day that we changed homes. Could there be something weird with the wiring in our new home which is causing this issue? Also, how is it possible that I'm able to access the Internet while not being able to access my router/DHCP server?

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#2 thrillhouse

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Posted 15 November 2010 - 02:35 AM

in the configuration page, try changing the lease time to the shortest time you can think of and see if that helps.

#3 BenGalaxy

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Posted 15 November 2010 - 06:50 PM

Thanks for the suggestion. Unfortunately it didn't work.

Originally the lease time was set to 0, which denotes 1 day. As one of my earlier troubleshooting steps I changed it to 9999 minutes, which had no effect. Per your suggestion I changed it to 1 minute. Unfortunately, no change.

Any other ideas?

#4 thrillhouse

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Posted 15 November 2010 - 07:00 PM

Have you looked at the tcp settings for your wireless card or ethernet? Make sure they are set to automatically obtain instead of a given ip.

#5 Orecomm

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Posted 15 November 2010 - 08:28 PM

Is it possible that the connection from your modem to the router is plugged into one of the (usually four) LAN ports on the router rather than the one WAN port ? If so you will have duelling DHCP's and your router will be trying to serve addresses to the entire subnet of the Internet that your modem is connected to. You can check the DHCP address you get on your other machines and make sure they are all in the subnet that your router thinks it is handing out. I've seen this happen more than a couple of times...




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