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Our internet router often stops working at home, but for the the second time only I have got a pop-up error saying:

"another device is using your ip address".

We have an iPhone and a Macbook but as far as a remember this problem occurred for a brief time when we were without an iPhone. In any case, I had a look at this post which suggests the problem is a cause of the iPhone and Macbook trying to use the same address.

I changed the IP address via System Preferences > Network > TCP/IP > configure IPv4 Using DHCP with manual address to 11.11.11.11. I then switched back to Using DHCP and clicked 'Renew DHCP Lease'.

When I checked the IP address again it changed to 192.168.1.11. It works now but I wonder if this is a permanent fix or will this problem keep occurring?

Update: The problem persists, but his time without the error message which would leads me to believe that there another problem in addition to the "Another device is using your ip address" problem.

  • What fixed your initial problem? – dan Dec 9 '13 at 15:20
  • Changing the ip address as explained above fixed the problem of "another device is using your ip address". But the router continues to stop sending wifi signal quite often. When this occurs, the TV still works as does accessing the router with a LAN cable. – nicholaschris Dec 9 '13 at 15:30
  • So your problem isn't really fixed, is that right? What make you think your wireless router stops sending signal? – dan Dec 9 '13 at 15:52
  • Correct, the real problem is not fixed. The wifi connection will be lost and then the wifi network will not be in the list of available wifi networks. Unplugging the router sometimes helps but it doesn't always work for long. As far as I can remember this problem started happening when I got my new work Macbook. Any ideas? – nicholaschris Dec 9 '13 at 15:57
  • Your problem looks much more like a wireless network with intermittent connectivity causing wrong DHCP attributed addresses. To help you to diagnose your problem, please provide some physical description of your wireless landscape: distances, connected equipments, 802.11g or n, channel used. – dan Dec 9 '13 at 21:45
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Often times these issues can be solved by rebooting ALL computers (iPhones, Macs, etc.) on your local LAN. A reboot causes DHCP to request a lease. And your router should only hand out ones that are unused. So every device should get a unique address

HOWEVER it is possible that you have manually assigned an IP address to one or more devices, so check for that. Make sure all are different and all are on DHCP.

ALSO possible, someone unwanted is on your network. Change the WiFi password just in case.

Failing all of that assign everything a static IP address like this

192.168.1.x

Where x is as follows

between 2 and 254 unique (only one device has any one number) Your subnet mask is likely 255.255.255.0 Your Gateway is likely 192.168.1.1 (your cable modem or WiFi access point) Your DNS will vary

The last three should be listed in your network System Preference and will be the same on all devices (only the IP address must be different). Select the connection (WiFi) and click Advanced, then the TCP/IP and DNS buttons. Record the subnet mask, gateway and DNS servers. Then fill that info in on all devices.

It would be a good idea, if you do this, to make a note of all the settings and which device gets which address. Keeping track can be a pain, which is why we have DHCP. It is supposed to hand out all that info automatically. So it is likely that there is a device on your network NOT set to DHCP.

  • 1
    The router may also hold the info of what device is currently using what IP. – markhunte Dec 9 '13 at 9:23
  • If you want to play it the "reboot way", then you have to reboot all your computers, all your AP (access point) which might also be playing the role of DHCP routers (iPhone configured to share their connection are providing this function). This might a lot of a reboot valse. And… unfortunately won't let you understand the problem. – dan Mar 29 '15 at 13:51
  • The hypothesis of a network intruder and mixed DHCP and fixed addresses are correct and to be investigated. – dan Mar 29 '15 at 13:52
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Check on your router which other computer or phone is using your IP address. Note your actual address, let's say it is 10.0.2.1. Look at your router ARP table and note the MAC address associated with your IP address 10.0.2.1.

If this MAC address belongs to one of your equipment

then everything is OK. Just check that this equipment is actually within reach of your router and make it renew its DHCP lease. For example on an iPhone, if your home network is named home_Wi-Fi this is:

Settings > Wi-Fi > home_Wi-Fi > DHCP > Renew lease

If the same IP address is regularly attributed to 2 different equipments connected through Wi-Fi, this may be caused by a poor quality wireless connectivity. Here is the scenario which might be at play:

  • 10:00 alice get address 10.0.2.1 from the router, with a lease time of 4 h
  • 10:30 alice goes in the living which is on the border of the wireless network and loose her connexion, but she doesn't care because she is just wotking on a heavy presentation with Keynote
  • 14:00 the router expires the lease attributed to alice
  • 14:30 bob ask a new DHCP address to the router and get 10.0.2.1
  • 15:00 alice goes in the kitchen which is inside of the wireless network and automatically use her actual IP address which is still 10.0.2.1

    ⇒ duplicate IP address detected

If this MAC address doesn't belong to one of your equipment

then you have a neighboor who is hacking your network.

In such a case, I advise you to fire a new interesting question:

How to get rid of my wireless scroungers?

  • The Alice scenario doesn't sound right. Once Alice loses her connection (but also anytime after her device's DHCP lease expired), her device would/should try to renew the IP address it had or else ask for a new IP address before doing any traffic on the network. – Marnix A. van Ammers Mar 29 '15 at 2:58
  • The first IP paquets emitted by alice (most probably a ongoing HTTP connection) will have the originating IP address previously attributed through DHCP. This is sufficient to be detected as a "duplicate IP address". – dan Mar 29 '15 at 13:46

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