DHCP problems

[rebootd]

I am running into a recurring problem: very often when I connect DHCP cablemodem clients to the internet, (a very busy DHCP server, btw)- I cannot get an IP from it. I can take one computer, put it on the same connection, and get an IP immediately. Then I take that one off, put the other one on, and ipconfig/release and /renew, reboot, reboot the modem, check network settings for the fifteenth time, etc etc and still get nothing but zeros. The error message I get is that the DHCP server is unavailable, or that it timed out.
Then, I can try the other computer again: even ipconfig/release all, then /renew, and it gets an IP immediately again. Can someone tell me if there is a hidden DHCP or network setting somewhere, maybe in the registry, whatever, that I do not know about?? This has happened with all desktop Windows OS's, although the scenario I just described happens regularly with both machines having the same OS at the same time. It *seems* as if it happens more often with Windows XP, although that may be just because more people own XP now. The NIC's are always working correctly when this happens: cables and hardware are always the first thing I check, and I can ping the loopback address just fine. Somebody please help?

 

[SgtB]

That DHCP server...how busy is it?

Also, can you run an ipconfig /renew on a machine over and over again...will it eventually get an IP address?

 

[rebootd]

Well, I know the DHCP server is very busy - I work for the ISP. However, it doesn't explain why I can get an IP for one computer and not for another. One of my problems is that I have to exhaust all other options first before I can go to our network guys and complain about our server! I have decided even to set up a test DHCP server with a crossover cable on a laptop to bring into the field so I can check to see if it really is our server or not. (At this point I do not think it is - I think it is something wrong with the client)
As to your second question: *sometimes* I run across a machine where that is the case, however this is not often, maybe one out of five problem cases. The rest refuse to /renew. And again, then why should another computer be able to gain an IP immediately, and another not? There must be something I am overlooking. It has been suggested that it might have something to do with the duplex settings on the NIC card. Anyone?

 

[SgtB]

The duplexing might be something to look into. Most cards are auto-sensing, and I've never really had any problems with those.

One great way to test this would be if you could set aside a couple static IP's that you could put on problem clients. Just to see if they can see the internet or the rest of your ISP's network. That way you can rule out the "not having and IP" problem on the machine, and concentrate on other avenues of troubleshooting. (IPconfig/cabling/network cards/duplex settings)