Another device on the network is using your computer’s IP address
This is a rather strange error message, you’ll get the notification “Another device on the network is using your computer’s IP address” and then you’ll lose internet access with the dialog box telling you to try connecting again later. No thanks, we need internet access now! So what causes this and how do we fix it?
It looks to be a problem with the DHCP server, which mistakenly assigns the same IP address to two devices, but don’t blame your router quite yet. For whatever reason it seems that the iPod touch, iPad, and iPhone is often the culprit, it seems these iOS devices like to maintain the same IP address and will attempt to force themselves onto the same IP that they had previously been assigned.
The easiest solution is to just reset the router, but that can be a pain depending on your access to the router itself. If resetting the router is a no go, you can renew your DHCP lease in Mac OS X either through the command line (as the linked article shows) or through the Network settings System Preferences. The other option is to manually set an IP address and have the IP range be far enough apart so that the devices do not conflict.
I assume this is just a bug with how iOS interacts with certain routers DHCP management, it happen to Apple’s own Airport too so perhaps that will spur a patch sooner than later. In the meantime, try one of the fixes, they should get your Mac back online in no time.
Warning about Spoofed MAC addresses
Another possibility (although much less likely) is that someone has managed to spoof your MAC address and IP and is attempting to gain access to your network. I say this is much less likely because assuming you have some reasonable wireless security precautions in place this is very unlikely, there simply aren’t that many people out there with the knowhow to crack into a secured wireless network. The other reason this is less likely is because this problem can be semi-reliably reproduced by simply rebooting an iOS device on a network with only 1 IP assigned (usually 192.168.0.1 or similar). Bottom line: if you see the ‘Another device has your IP’ error message, don’t freak out, it’s probably not a security breach.
A device cannot ‘force’ a DHCP server to use the same address. If a device has the same address over and over it’s because the lease didn’t expire yet or because the DHCP server remembers the device and tries to reassign the same address.
If a DHCP server hands out double addresses that’s not because the device wants it but simple because your DHCP server fails. A reboot often helps but that’s a workaround. You should consider using another DHCP server if such things happen often. Say once every few days or more.
What is the difference between ‘did’ and ‘has’? – Aah! ;o)
Using a drive image to set up several computers on a network can result in the same ‘computer name’ in the Sharing system preferences for several computers. Some DHCP servers expect unique computer names to assign different IP addresses. Finding the same name, the server has no choice but to try to assign the same address to the machines with the duplicate names. Each new login attempt produces the ‘same address’ error message and/or kicks the other user off the network. The usual remedy is to either assign a unique computer name to each device or no name at all so the server will default to using the computer’s MAC address to determine identity.
Problem: You see the message “Another device on the network is using your computer’s IP address” and you can’t connect to the Internet. In my experience, this only happens when running Apple’s AirPort on a wireless network. The problem is eliminated by using AirPort Utility to change the “Connection Sharing:” option to “Share a public IP address”. Here’s how it’s done (using my wife’s new iMac and AirPort Extreme wireless router as an example):
(1) Turn on your modem and your router first, and wait until they have talked to each other and your router has a steady green light.
(2) Turn on your computer.
(3) Click on your Applications folder.
(4) Inside the Applications folder, click on the Utilities folder.
(5) Inside the Utilities folder, click on the AirPort Utility icon.
(6) One of the window panes at the left side of the AirPort Utility display should show your router with a green light.
(If the light is not green, check your router. WARNING: Any time your router is working properly, but you don’t see it in one of the panes, you need to restart your computer and return to step 3, above.)
(7) Double click on the pane that shows your router.
(8) Click on the Internet icon.
(9) “Internet Connection” should be highlighted (rather than “TCP/IP”, etc.).
(10) Set “Connection Sharing:” to the “Share a public IP address” option. (“Connection Sharing:” should NOT be set to either of the other two options.)
(11) Click on the “Update” button, and then click on the “Continue” button.
(12) Close AirPort Utility and — most important — restart your computer.
With any luck at all, AirPort will behave itself now, and you will be able to connect to the Internet.
Gene Ledbetter
I’ve been trying to solve this problem for a few days now, and your solution was the one that finally worked. Thanks much!
Gene-
Thank you so much!!! You’re instructions worked!
-Caitlin
I have a linksys router and a cable modem. I cannot use the airport utility. (It doesn’t find a modem). Any other ideas? I get this message once a week or so. I also am having problems with my internet connection cutting out off and on.
I went through these steps but when I clicked update (#11 in your instructions), I get the following message in a window:
“Correct the 2 problems below before updating this AirPort wireless device
DHCP Beginning address
DHCP Ending Address
The DHCP range you have entered conflicts with the WAN IP address of your Apple Wi-Fi base station”
It then allows me to change the last segment of the DHCP Address, but doing this loses my Airport connections.
Any suggestions?
I got the message on our Mac server today.
The server is on a well secured, wired LAN network and behind a proxy server.
Our local network (3 mac-pros connected to the mini-mac server) immediately crashed.
but i don’t think this is a serious problem…
as long as no one else is sharing my stuff..
Im still havin trouble ive tried the steps but when i get to step6 it shoes no green light i have no router just a box woth two antenas not sure if its the router lol the apartments i live in provides the net. Ive tried unplugin it but to no avail pls help i have macbook pro running of just wireless with full bars but it goes in n out an gives the device network ip already in use warni g!!!!!!
[Ultimate Solution To This Problem]
Go to System Preferences > Network > WiFi Must be selected then click Advanced button.
Under TCP/IP tab set “Configure IPv6″ to “Link-local only”
Click OK button. Your Done!
Try to sleep/shutdown your mac, when it wakes up try to surf. Your already connected.
You don’t have to reset/turn off and on your router.
Tested on:
MBP 13″
OS X Lion 10.7.1
2.4 Ghz i5
4GB RAM
Thank you!
This worked for me when trying to connect with a new install of Lion on a second machine.
I am having just about the same issue as Suzanne (11/29/2011), but the message only started popping up tonight. If anyone has feedback for her or myself, I’m sure we’d both greatly appreciate it