Windows IP Conflict message.

dragon · 23-03-2011, 22:40

Is there anything apart from an actual IP conflict that can cause windows XP to display the message about having an IP conflict with another machine on the network?

Had a machine that was complaining of an IP conflict earlier but to the best of my knowledge there wasn't one.

I checked the DHCP server and it was showing the IP as correctly allocated to that machine.

I checked the ARP tables on the switches and the internet gateway/router and couldn't find any duplicate entries for that IP address. The ARP table has the correct MAC in it against that IP address

I also ran arping -b -I eth1 <ip> from a Linux machine on the same Lan

I only ever saw one MAC address responding to the broadcast arp and it was the correct MAC of the NIC in that machine.

Disconnected the machine with a ping and arping running and the responses stopped as expected.

haydnwalker · 24-03-2011, 09:47

could be the windows machine misreporting. Disconnect the network cable, reboot and try again?

Depends what the IP Address lease times are too. if they are 24hrs then they won't be given up until AT LEAST 12 hrs. You could try re-installing the IP Stack on XP?

---------- Post added at 09:47 ---------- Previous post was at 09:45 ----------

http://www.online-tech-tips.com/comp...lready-in-use/

See link (point 4 may be relevant)

dragon · 24-03-2011, 15:48

Quote:

Originally Posted by haydnwalker

could be the windows machine misreporting. Disconnect the network cable, reboot and try again?

Depends what the IP Address lease times are too. if they are 24hrs then they won't be given up until AT LEAST 12 hrs. You could try re-installing the IP Stack on XP?

---------- Post added at 09:47 ---------- Previous post was at 09:45 ----------

http://www.online-tech-tips.com/comp...lready-in-use/

See link (point 4 may be relevant)

I ended up forcing the DHCP to give it a new ip address (set an address reservation)

The PC only had 1 Nic so unless it had a 2nd one in the past (certianlly possible) I doubt it was conflicting with itself.

Kymmy · 24-03-2011, 15:52

Ahh, yes, when you change nic or remove a nic it still holds the details for the LAN, hence you get LAN #2, Lan #3..etc..

In device manager go VIEW >> Show hidden devices and clear out the old lans

Web-Junkie · 26-03-2011, 21:44

Would doing ipconfig /flushdns help?

tweetiepooh · 28-03-2011, 17:29

I got this issue
1)Linux box powers up gets address.
2)Can't see router page so reboot router.
3)Linux box all OK
4)Boot Windows laptop - gets address
5)Linux box fine but Windows has issues
6)Reboot Windows, still have issues.

Eventually Windows reports duplicate IP, router shows Windows box has IP via DHCP, connections show 2 boxes with same IP.

The Linux box (wired) via switch didn't detect the router reboot, probably the switch in between masked it so didn't try to renew DHCP lease. Router didn't see the address already in use --> IP conflict and nothing spotted it until I plugged laptop directly into router, not via switch.

dragon · 28-03-2011, 19:45

Quote:

Originally Posted by tweetiepooh

I got this issue
1)Linux box powers up gets address.
2)Can't see router page so reboot router.
3)Linux box all OK
4)Boot Windows laptop - gets address
5)Linux box fine but Windows has issues
6)Reboot Windows, still have issues.

Eventually Windows reports duplicate IP, router shows Windows box has IP via DHCP, connections show 2 boxes with same IP.

The Linux box (wired) via switch didn't detect the router reboot, probably the switch in between masked it so didn't try to renew DHCP lease. Router didn't see the address already in use --> IP conflict and nothing spotted it until I plugged laptop directly into router, not via switch.

Sounds like rebooting the router cleared the lease table.

In my case that hadn't happened, DHCP is handed out by a win2003 box and the switches being used were L2 managed so I was able log into them and check their ARP tables.

papasmurf · 03-04-2011, 04:16

Is there a problem setting static IPs? Always the easiest and most stable option in my experience.

(I know there are many situations and reasons for this not to be practical but I'm assuming this is a 'home' scenario. Sorry i it isn't.)

dragon · 03-04-2011, 11:45

Quote:

Originally Posted by papasmurf

Is there a problem setting static IPs? Always the easiest and most stable option in my experience.

(I know there are many situations and reasons for this not to be practical but I'm assuming this is a 'home' scenario. Sorry i it isn't.)

Static IP's wouldn't be a good idea due to the number of laptop users joining/leaving the network.

papasmurf · 07-04-2011, 03:26

Sorry mate, like I said, I was assuming a home lan environment.