Device on network has same IP address

VioletChepil

Hello all,
I'm getting a message on my home network that another device has the same IP address as my computer.
I'm trying to sort that out and just wondering whereabouts to start on that!
Let me know if any tips or advice on getting started.

Pooh

What are the two devices? Usually, in a home network, this shouldn't happen as invariably most users go for DHCP handed out IP addresses.

Where this usually bites you is with devices used in a corporate setting that have been given a fixed Enterprise IP address (e.g. 192.168/16, 172.16/12 and 10/8) and used in a home network with the same Enterprise addresses.

Studulike

Hello there,

There are lots of complicated ways to explain your problem and even more to solve it but a quick and simple way that should get you out of your problem is as follows:

On your Windows desktop go to bottom left of your screen and if your on Windows 10 you should see a search box or if not select the windows logo and select search.

In the search box type command prompt. This should show a few options but normally the top option which has an icon that looks like an old DOS desktop. Right click on this and select run as Administrator. This will open a black coloured box on your desktop. This is your command prompt.

Next type: ipconfig /release (then press the return key)

Next type: ipconfig /renew (then press the return key again)

Then you can close that window and you should be left with your Windows desktop and your pc should now connect back to your network or router etc.

Let us know if that suited your problem, if not contact me directly and I will be happy to help you.

kltaylor

Quite literally you cannot have two devices with the same IP address on the same network.  There are network protocols to help prevent it, but in the event that you receive the message that the IP address has already been distributed, determine which devices are in conflict and issue a full cold shutdown.  That is, turn off the computer, count to 15 and turn it back on.  Disconnecting the AC cable isn't a bad idea either while it's powered down.
Alternatively, you can also force the device to obtain a new IP through an elevated command prompt or terminal window if its a desktop.

Systops5

In the future Violet, there are two ways you can look into this. 1. Use an app like Angry IP Scanner, and 2. Look at the DHCP settings in the Router. This "Should" allow you to see what devices have been given the duplicate IP addresses. Technically the router should never give out 2 IP's if all f your devices are using DHCP. If you have any devices set to manually configure their IP addresses, then those devices would be the first ones to look at as being suspect. The IP scanner can sometimes catch the devices with the same IP however, usually one or both devices will be offline as you can not have 2 devices with the same IP. Once you determine which devices have static IPS configured, you can then change them to DHCP, then the problem should be resolved. I usually only set static IPs on servers which rely on a static IP and leave the rest in DHCP.  Dont know if this will help or not but it does sound like you have resolved the issue.

kltaylor

VioletChepil said:

@Marc it could have been. Or a false message? It seemed to have resolved itself without any actions required from me. 

I don't think that it was a false message, rather one of the devices didn't process network services correctly and retained and IP address without requesting verification from the router/firewall.  It's not a typical thing that happens, which is why issuing a cold boot should fix the issue alone.

pwmeek

VioletChepil said:

These are two PCs causing the issue. But I'm not sure how to check. Do you know how I'd check this? On the router settings page?

You can check how each is getting its IP address by going into the network settings of the PCs (My Windows experience is long out-of-date, so you will need advice from someone using Windows for this). If one or both are manually setting their own IP address (which I suspect) you will have to decide whether you want an all-DHCP network or a mixed network: 

• If all-DHCP then set the offending PC(s) to use DHCP in their network settings. (It may be (it used to be, long ago) described as "Get your IP address from your router".)
• If you want (or have to have) a mixed network, then you will have to set the router/switch that issues the DHCP IP addresses to reserve a range of IP addresses for manually set devices (including any that are hard-set to a single IP address - not likely unless you have some very old equipment on the network). This will be a nuisance, because once you are done, you will have to do a cold restart on the router and all other devices (all off, then restart router, then all other devices one by one, allowing them time to reboot completely) to allow them to resolve a new set of IP addresses. You will also need to manually set the offending PC(s) to different IP addresses within the range you set aside for manually set addresses. Note that I have some experience with mixed networking since I tend to like certain devices to always have the same IP address, such as cameras and other devices that I want to make accessible from the outside world. It makes port forwarding easier.

VioletChepil

These are two PCs causing the issue. But I'm not sure how to check. Do you know how I'd check this? On the router settings page?

Pooh

Does your Fingbox not help? In theory, they're both on the network... How many PC's you have on your home network? 

Also, shouldn't this be a question? 

Pooh

This page lists out the various GUI'd ways to get the IP address of a PC: https://kb.netgear.com/20878/Finding-your-IP-address-without-using-the-command-prompt

kltaylor

VioletChepil said:

These are two PCs causing the issue. But I'm not sure how to check. Do you know how I'd check this? On the router settings page?

If its Windows 10, navigate to settings and then to Network & Connectivity.  But this is a slow way ... in Cortana type, CMD and press enter.  Once the dark 'Command Prompt' screen opens type ipconfig and press ENTER.  Look for the IPv4 address, that will be your internal LAN IP.

VioletChepil

Thanks all - the message mysteriously disappeared and never returned and now the Internet is working fine! 

VioletChepil

Thanks @Pooh I've changed that over to a question

Marc

Could this have been some dhcp issue where the same address was given before the original device released?

VioletChepil

@Marc it could have been. Or a false message? It seemed to have resolved itself without any actions required from me. 

VioletChepil

Thanks for the great answer @pwmeek - I'm so ready for the next time this happens!!