DHCP Problems...

[Paul Victorey]

OK, I am in charge of PC tech support for most of my office, but someone else is in charge of maintenence on our DSL/internet service, including a firewall and DHCP server.

My problem is this: Sometimes, computers will randomly be refused IP addresses. There is no immediately obvious cause: no settings would change, it would literally be able to obtain an IP one day and not the next.

This period, in which all requests for an IP address fail, can last for a day or for months. Trying to manually renew the computers (using ipconfig or winipcfg) returns the error "Access Denied: Renewing Adapter".

It is not a connectivity problem, at least not on my end -- the computers, which do not use TCP/IP for LAN connections, are still able to fully access any computer on the LAN. They just are not getting an IP address.

Now, I've brought up these problems with the person in charge of keeping the DHCP server functional, and they swear there are no problems with how it is configured -- and 99% of the time, the DHCP server DOES work.

It is also not a problem with having all available IPs leased -- I do know there are IPs available for leasing; that was the first thing I had the other person check.

This has happened, so far, to 2 machines running Win95 OSR2, and one running NT 4.0 SP6a. The other 10 PCs and the ~40 Macs on the network have never had problems, that I am aware of.

Any ideas as to what's wrong, or how to fix it? I've tried reinstalling TCP/IP, and tried reinstalling the NIC on one of the affected machines, to no avail.

[bob]

Probably not all addresses on the network are using DHCP. It just takes a few people to set a static address and as soon as a pc requests that used address it will fail.

Check event log on the dhcp server to see why the address is being rejected.

[Blankman]

I'm in the same boat with you Paul...I run a simple LAN and have just been using DHCP for the last two months but have run into several problems like yours and most have been on win95 machines even though some 2k machines seem to have minds of there own...I usually end up bringing down the entire net and back up again and let the server(router) dole out IP's again until someone has to reboot, or a machine goes down, then inadverdently I'm back on the same path.
Heck, I've known of DHCP handing out an IP to a printer not even in use on the LAN and causing a conflict with a server using the same IP...

[mbossman2]

agree with Bob. It is likely that there is a conflict with DHCP pool and one (if not more) static IP addresses.

Check the log and ensure that all the admin set static addresses are removed from the pool and make sure that no one has a static address that you did not give them.

[embrelleur]

try checking wich devices on your network uses static IP and removing those adresses from your scope

That can help

[fred]

I wonder about that too. I check DHCP now and then and often see duplicate list entries and general "mistakes" in the lists. I have had times when machines have been refused too. But mostly during times of "confusion" when machines are switched on and off quickly - I just wonder if it is a time issue, although I have to admit, I not an expert at this, at all!

[Allanv]

here is what i do
i set all leases to never expire that was once a pc has a ip it will not try to renew the lease as it knows its set to never expire...

also on my machine @ work it has the cable modem attached to it so i needed a static address so i manualy added this to my pc and then on the server i told it to exclude the address from the address pool the same as a printer and a print server ....

i have never had problems with ip leasing using this method


give it a bash cant harm anything now can it