Conflict between devices connected to the same router – Understanding IP addresses

Discussion in 'Mac Accessories' started by fstigre, May 21, 2010.

  1. fstigre macrumors regular


    Aug 12, 2008

    I have been using computers for a while now and I just realized that I don’t know something as simple as IP addresses. I’m correctly connecting my Notebook, my iPhone and a PC laptop to the same routing (wirelessly) and a few times I have seen a message in my Notebook saying that another device is already using the same IP address, I’m assuming is my iPhone but to really find this out I would like to have a better understanding as to how IP addresses are assign to this devices when connected to a router, if I’m not mistaking each device should have its own unique IP address and if this is true how in the world these two devices are interfering with each other.

    Can someone help me understand how IP addresses work? Something like…

    1- What is an IP address?
    2- How routers communicate to clients?
    3- Does the router assigns unique IP address to all devices connected to it, or it uses the device's IP to communicate?

    Can someone be so kind and explain this a little bit or direct me to where I can find these basics.

    Thanks a lot.
  2. Hellhammer Moderator


    Staff Member

    Dec 10, 2008
    1- It's Internet Protocol address. When you connect your device to router/modem, your modem will ask for IP address from the ISP and give it to the device.

    2. Do you mean ISP or devices?

    3. When you connect device, it'll ask for IP which is unique for the device. In your situation, the ISP can't provide more IPs or your router lacks support for X number of devices (you have too many).

    Hope this helps, not really an expert on this so please correct me if I'm wrong :eek:
  3. Darth.Titan macrumors 68030


    Oct 31, 2007
    Austin, TX
    Your router is supposed to get an external IP from your ISP. The router then shares this single IP by assigning each of the computers on your network their own individual internal IP addresses via its onboard DHCP server. In effect, to your ISP everything on your home network appears as one device - the router, your gateway device.

    The problems you describe can arise if you have one or more machines are assigned a static IP in their network settings, and that IP falls into the range used by the router's DHCP server. So make sure none of your machines have their IPs set manually. They should be set to get their IPs automatically by DHCP. If you do need to set a static IP for some reason, make sure and choose one that is outside the range used by the router but still on the same subnet. You can usually find out what range your router's DHCP server is using on its configuration screen accessed by a browser.
  4. fstigre thread starter macrumors regular


    Aug 12, 2008

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