unable to contact your DHCP server (from: ipconfig /renew)

[DaveF]

I have high speed cable service through Comcast. 99.9% of the time I have
my cable modem going through a router to share internet access with
multiple PCs. Every now and then I disconnect the router and directly
connect the cable modem to a PC. The process I use is ipconfig /release,
unplug the modem for a moment to cycle power, plug in the modem, wait for
it to boot, then ipconfig /renew. Usually the IP information comes up, and
everything works as it should. I've never had a problem with this until
today. Now after I enter ipconfig /renew, it hangs for a bit and I receive
the message ** An error occurred while renewing interface Local Area
Connection : unable to contact your DHCP server. Request has timed out. **
Strange, I did this the night before, and it worked as usual. After
spending much time cold booting the PC, unplugging the modem, rechecking
proper settings, even uninstalling zone alarm just in case, etc, I gave up
and went back to the normal configuration of having the cable modem going
through the router, and then connecting the pc to the router. IT WORKS!
Now why in the world can I NOT get the cable modem working directly
connected to the PC. All my network drivers and window updates are up to
date. I've used multiple cables, same response. I newsgroup google'd the
"unable to contact your DHCP server" error, but none of the solutions that
I've seen worked for me. I've called Comcast tech support and went through
2 levels of support. They told me they would send someone out, but they
couldn't give me a date because their February schedule is not available
until feb 1st.. ??! Does anyone have any suggestions? Any help would be
much appreciated!

-Dave

 

[CheshireCat]

Hi Dave
I don't know what to suggest to you aside from closing down the pc before
you turn off the modem, wait 30 secs then restart modem followed by pc once
the modem has finished flashing lights at you. Ours is NTL cable on a pace
modem and you just have to do this long winded operation to make sure the
modem's finished all its operations cleanly. Ive found it pretty much hit
and miss affair to get a connection if I veer from this path.
A possible useful diagnostic tool is sysinternals.com's tdimon which
monitors all tcp/udp activity. It produces a lot of log items but its easy
to find the udp dhcp requests among the other information

 

[WesternEyes]

OK Problem fixed. To anyone who encounters this problem and can't find a
fix anywhere.. the problem was the cable modem. Cable Tech came and
swapped out the modem with a newer one. Everything is back to normal.