Link to home
Start Free TrialLog in
Avatar of Mark Olivier
Mark OlivierFlag for United States of America

asked on

IP Address Conflict but Can't Release or Renw

I put a new (used) Vista laptop on a workgroup and it always gets "An error occurred while renewing the interface Local Area Connection:  The DHCP client has obtained an IP address that is already in use on the network. The local interface will be disabled until the DHCP client can obtain a new address".  The problem is that since the local interface is disabled, I can't release or renew the address.  Plus, I can't tell what the exact address is that is causing the conflict.  If I put in a fixed address it works fine, but goes back to having a conflicting IP address once it set to automatically receive and IP.  Since this is a laptop that will regularly be taken offsite, I can't leave it in a fixed IP state.  

This workgroup uses Server 2008 as the file server, but, as I said, this is a workgroup and not a domain.  The DHCP server assigned to the NIC is the modem/router IP, not the server, and that is also the DHCP address the other computers are automatically assigned.  Because this is a new site I'm not yet fully familiar with, I'm not sure if the server is set to also be the DHCP server.

This laptop has a fresh installation of Windows.  It was reinstalled at my shop, which uses a 10.0.0.x addressing scheme and we had no trouble picking up an auto IP address there before I brought it to the client site.

Does anyone have any suggestions how to get this machine to pick up a non-conflicting IP address?
Avatar of Imal Upalakshitha
Imal Upalakshitha
Flag of Sri Lanka image

check DHCP server whether there is an static IP reservation for specified client's MAC
I guess that DHCP server is trying to assign to your laptop IP address which is already set as fixed IP address on another device.
If the DHCP server would be on Windows server, it would be easy to check what IP address is assigned to your laptop. But I don't know what capabilities has your current DHCP server.

One option you have is to use some IP scanner (like angry IP scanner to check used IP addresses in your network and set DHCP range outside used IP addresses or make exclusions of used IP addresses out of DHCP scope.
The issue is caused by a dhcp flag error on the issuing device.

Please see KB:  928233

They have a "fix it" for this issue.
the reason you can't do a release / renew is because you haven't been given a good ip address yet. Your machine is in limbo waiting for the dhcp server to give your machine a valid address. about all you can do is set a static address and hope that it isn't in use.. until you can query the dhcp server and find out what is going on.. perhaps using wireshark and limiting it to dhcp would give you a better idea of what is going on.
Avatar of traoher

Find out the IP, unplug the troubleed computer, ping that IP that was in conflict see if anything replies to it.  If so, goto the DHCP server and exclude that IP from the DHCP scope.
Run ipconfig and see what the IP that is being assigned.  Note the event log will reflect the MAC address of the system with which there is the IP contact.

You can look as suggested at the reservation list for the MAC address in question.
You can then also access you switches to identify the system that has the MAC address and look at what the reason why you have an IP being allocated by DHCP and is being in use by another system.
Avatar of Mark Olivier


Thanks for all the excellent suggestions.  Because the location where that laptop is is currently closed, I may have to wait until next week to try the different things mentioned above.  I can access it remotely, but once I set it to Auto IP, if it doesn't assign correctly I won't be able to access again until next week anyway.

I did find this over and over again in the laptop event log:
"Your computer has detected that the IP address for the Network Card with network address 001DBA2134F1 is already in use on the network. Your computer will automatically attempt to obtain a different address".  This makes it seem as simple as the laptop pulling a new IP, but it doesn't do that.  I also don't think there are static IPs on the network, but I'll double check that when I can.

One of the events also said something about a computer with a duplicate name, but I'm absolutely certain there's no computer with the same name on the network.

I will post back when I implement some of these suggestions.
Is the laptop you use a Sony?
Ping the IP and then run arp -a
Locate the MAC address that reflects the
Use that information on to identify the manufacturer of the NIC in an attempt to identify the system.

If these are domain computers, you could try running the command
systeminfo /s \\ to see what system has this IP.
Others pointed to look at your DHCP server to make sure the IP is not reserved.  It is possible that someone has defined that IP as static while the DHCP is still allocating it.
Exclude the from being allocated and that should resolve the issue with this laptop, but you should still identify the system that is using that IP to make sure it is not an unauthorized system that someone connected to your network.
Avatar of traoher

Link to home
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
Start Free Trial
Traoher, you might be on to something.  This is an AT&T DSL line, and it does have a standalone modem without the built in router. I saw the modem and a Cisco switch under a cluttered counter and assumed the router was behind those, but maybe it's not.  Maybe there isn't one.  I'll find out Wednesday when I go back over there.
As traoher suggested, the address was given out by the AT&T modem, which is plugged into a switch.  This modem is apparently not a fully functional router and does not have the ability to issue more than one IP.  There was, in fact, no other router in the mix and DHCP in the server is not turned on.  Thank you all for the excellent suggestions.