What is the reason for Windows IP address conflict?

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I get this message once in a while when using the Internet from a PC with Windows 7:

Windows has detected an IP address conflict.

Image of the error:

enter image description here

Thanks for any pointers.

Vasudev Ram

Posted 2014-07-19T21:12:50.397

Reputation: 93

3The description is fairly spot-on. There’s another device with the same IP address on your network. As such, please tell us more about how you access the internet, whether DHCP is used and which other computers/devices are on your local network? – Daniel B – 2014-07-19T21:37:12.050

3Yeah, are you using DHCP or static addresses on your network? If you are using DHCP, there might be a static DHCP lease configured on the router with a mac address that is different from yours, but if your machine is set with a static ip address this sort of error would be the result. Do you have access to the administrative interface on the router you are using? – Richie086 – 2014-07-19T21:52:34.913

Thanks for the responses. Will check these points and update the post in a couple of hours ... – Vasudev Ram – 2014-07-20T12:55:59.160

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As such, please tell us more about how you access the internet,

– Vasudev Ram – 2014-07-20T14:31:49.330

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As such, please tell us more about how you access the internet:

I use one of two methods:

  • DSL line
  • 3G USB wireless modem

Sometimes the DSL line is on (but not working well) when I try to connect via the wireless modem. At other times I use the wireless modem alone, while keeping the DSL line off. Not sure, but I think this error happens more often (or solely) when both are connected. Yes, I think it is DHCP. Not sure of the exact command to check this on Windows 7, but I did "ipconfig/all | grep -i DHCP" and it shows many lines, some with "DHCP enabled...YES" and others with "No." – Vasudev Ram – 2014-07-20T14:38:10.307

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which other computers/devices are on your local network?

There are no other physical computers or devices on my local network. But I do have VirtualBox installed on Windows. And I have a few virtual machines setup on it, for development purposes. I start the VMs when I work. Can't remember now whether the IP conflict error happened when a VM was running or not. A couple of the VMs have virtual networks configured so that I can communicate between the Windows OS and the VM (Linux). e.g. I access the Flask app I am developing on the VM, from the Windows command line with curl. – Vasudev Ram – 2014-07-20T14:40:33.350

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Yeah, are you using DHCP or static addresses on your network?

I think it must be DHCP because of the above mentioned DHCP messages in the output of ipconfig/all. – Vasudev Ram – 2014-07-20T14:41:41.193

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Do you have access to the administrative interface on the router you are using?

I think I may have. The vendor set it up some time ago and configured the router via the browser on my laptop. Will need to check the details of how to do it, e.g. the IP address, I had saved it somewhere or can ask him. – Vasudev Ram – 2014-07-20T14:43:27.580

P.S. Had to put my answers to all the questions using multiple comments, because of comment size limitations. – Vasudev Ram – 2014-07-20T18:28:37.130

is this your own private network, or do you have a network admin you can ask? if you are at home, then continue, if you are at work or school, then ask your network admin for help. PS: dhcp... us it :) – Sverre – 2014-07-21T04:34:38.807

user1201232: this is my own private network - not even really a network, except for the VMs' virtual network configured on Windows - apart from that only my laptop and DSL modem-cum-wifi router are on the network - okay, sometimes I do use my Android phone with the wifi instead of with the mobile data plan I also have. No company network admin who I can ask, unfortunately - I work from home. DHCP is being used as I said above. I did not apply for a static IP address for the DSL line. Thanks for the reply. – Vasudev Ram – 2014-07-21T09:09:00.713

Answers

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Introduction:

If you have DHCP enabled on your router, then it assigns every device that makes a DHCP request a unique LAN IP address. If there's a device on your network that has DHCP disabled (static IP assigned to it) it will not request a DHCP IP. So what happens is this:

You have a device that initiates a DHCP request to your router, say it got the IP x.x.x.2, then afterwards you (or someone) have powered on or connected a device that that was otherwise powered off or disconnected; that recently-connected device has DHCP turned off and is statically assigned x.x.x.2 in its network settings, so now you have two devices with the same LAN IP address, and there's the conflict.

Solution:

Go to your control panel > Networks [something] > Network Connections > right-click your active network (wireless or local area) > properties > Networking tab > look for "Internet Protocol Version 4" choice on the white scrolling box > click it > Continue on one of two cases:

1- "Obtain IP address automatically" is chosen > SOLUTION: just reconnect to your network (disconnect and connect again)

2- "Use following IP address" is chosen > SOLUTION: either change the last number in the IP address field (first line) or simply chose the "Obtain IP address automatically"

Mars

Posted 2014-07-19T21:12:50.397

Reputation: 282

Mars: Thanks, will try that out and then reply here in a few hours. – Vasudev Ram – 2014-07-21T09:10:26.720

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1- "Obtain IP address automatically" is chosen > SOLUTION: just reconnect to your network (disconnect and connect again)

"Obtain automatically" was already chosen. The conflict problem is not happening now, so I can't check it by reconnecting. Will try again later if and when it happens. Thanks for the help. – Vasudev Ram – 2014-07-21T16:30:06.653

1Reconnecting means you'll request another (new) DHCP request (so you'll get an unoccupied IP), thus when you turned your computer off and on (or simply the computer might have disconnected) you already got another IP. Now since "Obtain IP address automatically" is chosen, I can almost be sure there's another device on your network with static IP setting ("Use following IP address" method) – Mars – 2014-07-21T17:49:04.047

Thanks for the reply. Could that other device with a static IP address be the router itself? If so, how should I check for that? As I said above, I did not ask for a static IP address when buying the DSL connection, but don't know enough to know whether there is such a thing as an "internal static IP address" that may have been assigned to the router by the vendor, even though I did not ask for an external static IP address. – Vasudev Ram – 2014-07-22T13:56:12.750

1We're talking about LAN here, you don't need to worry about your DSL or external IP, just the IP that your router assigns to each device on your local network. That configuration is in your hand, and vendors has it set to DHCP by default. As for the router having a static IP, then that's right, routers usually have the first IP slot in the subnet, so router gets x.x.x.1 (you can find this out by looking at the "gateway" field in your Windows 7 network configurations(Network Connections)>Network details, that's is normal. The occupied static IP is taken by another device which is not the router – Mars – 2014-07-22T17:44:39.697

Thanks for the reply, though I'm only seeing it now :) – Vasudev Ram – 2016-12-17T14:06:04.877

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  1. go to Control Panel\Network and Internet\Network and Sharing Center.
  2. disconnect network.
  3. click icon of network rightmost.
  4. set network properties will appear.
  5. click merge or delete network locations.
  6. in dialog opened if possible delete all network locations.
  7. close dialog.
  8. List item
  9. now connect network.

manjunathmayur

Posted 2014-07-19T21:12:50.397

Reputation: 1

1Please read the question again carefully. Your answer does not answer the original question, which asks "what is the reason ..." – DavidPostill – 2016-12-16T10:39:32.230

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One of the computers on your network has an ip address manually set (static) in the tcip/ip settings for one of the network cards. It's simply a case of finding the culprit and setting it to dynamically get an ip from your router. This assumes you're on a small network. On a large network you could be in for a headache lol.

Codezilla

Posted 2014-07-19T21:12:50.397

Reputation: 828

Asked: 2014-07-19T21:12:50.397

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Active: 2016-12-16T06:41:25.870