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ipconflict

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by shippauf

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I have a couple of users that are continuing to experience ipconflicts w/in our network. We currently have a WIN 2K PDC, with 3 NT BDCs. I have replaced the NICs in the PCs affected from a 3CSOHO to 3C905B-TX and 3C905C-TX cards. I have also changed the switch ports that the users are attached to. We are strictly a DHCP network w/ no static IPs w/in the scope.

Anyone have ideas as to why I received ipconflicts in a DHCP environment?

Thanks.

5 replies

by mike o

Replacing the NICs shouldn't matter, as they all have different MAC addresses anyway. Which machine is handling the DHCP chores? Make sure you are only using one DHCP server or you're going to get conflicts like that.

Also, your PDC and BDCs should be statically-assigned, ideally. Especially whichever server is doing DHCP. Then make sure the scope of IPs being handed out does not include the static IPs of the servers.

by shippauf

Sorry, didn't mention that the servers are all statically assigned and yes their ip's are not included in the scope. I tend to agree with you regarding the use of only one DHCP server but my outsourcing consultant indicated to us that since we are running in "mixed-mode" that we MUST keep the old DHCP server (NT4) up and running with DHCP enabled so that NON 2000/XP clients can authenticate. And again, this is only occuring on a few clients.

by timwalsh

It sounds like the problem is continually experienced with the same PCs. What else is in common with these PCs?

In a DHCP environment, IP conflicts most often occur when you have multiple DHCP servers with overlapping scopes (i.e. trying to offer the same IP addresses). But this would cause problems across your network, not just with certain PCs.

Less often, you may see IP conflicts occur if you have long duration leases and one or more PCs are disconnected or not turned on for an extended period of time.

If a PC's BIOS clock is wrong, it may not realize that it's DHCP lease has expired when it actually has.

by holdenburg

Hi...
Check your scope. Win2k server can take additional ip addresses when using different services. If your scope is not large enough to accomadate your existing lan then you have an issue. Also, reserve your server ip address within the scope to make sure that DHCP does not hand out an ip address that is already in use with a static ip addresses of your server(s).

Good luck...

Herb

by russell.brown

Check the lease times and reduce them down to 8 days, also check that if your running multiple scopes on 2 servers acting as dhcp servers that they are trying using the same scope

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