IP Conflicts

[sdkramer]

Ok I've got a couple machines that are getting IP conflicts on our network. When I get to a machine with a conflict they are obtaining an IP automatically as they are supposed to, but if they are getting them from a DHCP server either it's configured incorrectly, or there is another DHCP server. My questions are 1. Is there any other reason to get this problem? 2. How can I scan the network for DHCP servers? 3. If I find none does my problem have to be a poorly configured DHCP server?

TIA,

Seth

[christo418]

If you are the system administrator, you need to figure out which server is your DHCP server, and you do that from the server side and not the client side. The range of IP addresses may be in conflict with static IP (for instance: router interfaces, network IP addresses, or network printers). Pretty easy to figure out, as long as you have access to the machine that is handing out the addresses. hope this gives you a starting point. Also, systematically check all servers to see if this service was default started by mistake.

[sdkramer]

This is my problem. I'm not the admin, I'm just a lackey. But my admin refuses to admit there is a problem. Does anyone know the name of any scanning software that could tell me this information?

Thanks

Seth

[obyteme]

Let's start from the beginning so we know what to look for. First what is the error message you are getting? Is it "this address is in use by another machine" or "unable to obtain an IP address".

[sdkramer]

IP conflict with the address 10.162.x.x (campus ip address) with the hardware address 0E:2B:56:...

[obyteme]

Wait a sec did you say that you get this error message all the time on these two machines only?

Here is what I think is happening...the only machines that are going to have an assigned IP in a network is usually a printer, router or switch. I think that this problem is more than likely a printer that has an IP that should have been removed from the pool of IP addresses that you are pulling from. This is an admin issue pure and simple. Write down the IP address and the MAC (hardware) address from the error message and give them to your admin, he should then track down the device that has that IP and then remove it from the IP pool. Hope this helps.

[sdkramer]

This happens routinely amongst random machines on our 1200+ node network

Thanks

[Great_One]

it almost sounds like you have multiple dhcp servers that are
configured with over lapping scopes. you need to consult the network admin
to get the information on the dhcp setup.

[obyteme]

Great One has nailed it. On a large network that is probably the only thing it could be.

[bob]

http://coffer.com/mac_find/ may give you a hint as to what it is. Also nbtstat at the command prompt will give the machine name. Telnet the Ip address will find out if it is a printer/switch/router etc. Ftp the ip address too.
If nothing above works it is bad DHCP settings or dos network drivers and a static address.