Previous 1 2 Next 21 Replies Latest reply: Mar 3, 2011 9:27 AM by MacDenney
MacDenney Level 1 Level 1 (0 points)
Occasionally, this dialogue box appears when awakening my iMac. It says:

"Another device on the network is using your computer's IP address (10.0.1.20)", and
continuing in smaller print: "Try connecting again later. If you continue to have problems,
change the IP address of this computer or the IP address on the other device.
Contact the network administrator if you need more information".

I have this Mac, a Mac Laptop, an iPhone, and an iPad connected to my Airport Extreme. What can I do to eliminate this box? It doesn't seem to effect anything when I click "OK", and it disappears. It's just annoying!

latest gen. intel iMac, Mac OS X (10.6.6), 500 gig HD, 4 gig RAM, superdrive
  • Linc Davis Level 10 Level 10 (169,225 points)
    The protocol that assigns IP addresses automatically (and makes sure they're unique) is called DHCP. Enable the DHCP server on your base station, and set all the clients to get an address from it.
  • MacDenney Level 1 Level 1 (0 points)
    Thanks for responding!
    Now . . .how do I go about "enabling the DHCP server" on the Airport Extreme Base Station?
  • Linc Davis Level 10 Level 10 (169,225 points)
    Launch AirPort Utility, select the base station, go into Manual Setup. Select the Internet page of the settings. Select the Internet Connnection tab, and from the Connection Sharing menu, choose "Distribute a range of IP addresses." That will cause the AEBS to act as a DHCP server on the local network.
  • Camelot Level 8 Level 8 (46,440 points)
    The protocol that assigns IP addresses automatically (and makes sure they're unique) is called DHCP. Enable the DHCP server on your base station, and set all the clients to get an address from it.


    That is too vague an answer to be practical.

    For one, the likelihood is that the DHCP server is already enabled in the AirPort Extreme - or, at least there's already a DHCP server running on the network. If it's already running then 'enabling it' is not going to help. If it's not already running then you just enabled a second DHCP server in the network which is going to cause even more problems.

    Besides, you cannot easily "set all the clients to get an address from it". DHCP uses a broadcast protocol to find DHCP servers and, generally, whichever server responds first is the one the client will use. There's no client-side way to tell any given device which DHCP server to use.

    Besides, as described, it's not even clear that the IP address is even in use by another DHCP-based client. It could be some other device on the network (printer, maybe?, Blu-Ray player? PS3? X-Box? or even some rogue client) that's configured with a static address.

    The actual solution to this problem requires some troubleshooting. You'll need to start off with the base station - it will give you a log of the connected clients listed by MAC address and assigned IP address. Cross reference this list with the known devices (Mac, iPad, and iPhone) and you may find the rogue device. Once you have the MAC address you can start to trace the device on your network.
  • MacDenney Level 1 Level 1 (0 points)
    Hello, didn't work as described. The page said that the range interfered with the base station.
    Also, I didn't see an "internet page of the settings".
  • MacDenney Level 1 Level 1 (0 points)
    Got it! Now, how do I find that "log of the connected clients"?
  • Linc Davis Level 10 Level 10 (169,225 points)
    Click the icon labeled Internet.
  • MacDenney Level 1 Level 1 (0 points)
    I have not been able to access this "client list" from the base station. I've use all the advice given in this thread, but still can't find this list. I've followed all the instructions so far; maybe they just need to be more explecit.
  • Linc Davis Level 10 Level 10 (169,225 points)
    You say you have a Mac laptop that's working properly on the same network. Please open the Network preference pane on that laptop, select the AirPort connection, and click on the "Advanced..." button. You now see a tabbed sheet. Select the "TCP/IP" tab. There's a menu labeled "Configure IPv4:" What is selected in that menu? Below that are some settings: IP address, subnet mask, router, DHCP client ID. What are those settings? What are the corresponding settings on the problem Mac?
  • MacDenney Level 1 Level 1 (0 points)
    Thanks for helping: LAPTOP: iPv4 - using DHCP
    IP address- 10.0.1.4
    subnet- 255.255.255.0
    router- 10.0.1.1
    DHCP client ID- none selected (if required)

    PROBLEM MAC: settings are identical EXCEPT for the IP address
    which is - 10.0.1.28

    Interestingly when the laptop was brought back close to the iMac (iMac sleeping) the same
    dialogue box appeared on IT?? But never appears when its in its usual spot at the other end of the house.
  • Linc Davis Level 10 Level 10 (169,225 points)
    That all looks correct. You have two other devices on the network (that you know of.) Please check their network settings. They should both be getting an address using DHCP, and their settings should be the same, except for their IP address which should be different. If that's the case, then please restart your AEBS and try again to connect with the problem Mac.
  • MacDenney Level 1 Level 1 (0 points)
    Hi Linc Davis;

    All the IP addresses are different. I restarted the AEBS and everything is working. Thanks.
    Hopefully that dialogue box won't reappear!

    MacDenney
  • Linc Davis Level 10 Level 10 (169,225 points)
    If it does, it may be that someone has cracked your network.
  • MacDenney Level 1 Level 1 (0 points)
    I guess that would mean activating some security measures. Got any suggestions?
    Never have used any before.
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