Two computerswith the same IP address?

Discussion in 'Apple, Inc and Tech Industry' started by Not Available, Jul 27, 2009.

  1. Joined:
    Jun 30, 2009
    Hi! Is it possible to have two machines with the same network specifications?

    The thing is I've got two machines, a PC and a Mac, and I wanted to connect to the PC remotely. I've taken the info from it, and found out it's the same with my Mac. The problem is, although they're both from the same ISP, their location is totally different, different neighborhoods, different modem types, etc. They're both wired, with Ethernet. Even the plans are different (4Mbps to the Mac, 20 to the PC). The only thing which is not different, is the one the services are sold/registered to.

    Also, they're both working awesomely.

    Is this normal?
  2. r.j.s Moderator emeritus


    Mar 7, 2007
    Two computers cannot share the same IP address. I'm not sure what you want to do here.
  3. crewrules101 macrumors member

    Aug 9, 2007
    More details please

    To help you out we need more info. If each of the computers are connected to the internet, then it is almost impossible for them to have the same IP. They might have the same IP coming from a router, for example,, or, but for them to have the same internet address is impossible. On each of the machines, go to and see what it says. They should be different.

    To remotley connect to them, if you are using a router, you are going to set up either NAT or DMZ. Apple routers use NAT, though some other brands may use it as well. Lynksys uses DMZ from what I remember.

    If they are connected directly to the internet, through the modem, all you should need is the IP address, and the port you are trying to access. That and a valid Admin password and username, and you should be good. If you are using a router, you will need to set up the router to forward a specific port to your computer so that it can be accessed.

    Again, more info is needed though to help you out to the fullest.

  4. bruinsrme macrumors 603


    Oct 26, 2008
    it sounds like a lease expired on the router but one of the machines did not accept the lease renewal.
    It happens on my network when I didn't have enough DHCP address available.

    In the past I have configured printers and desktops with static IPs and leaving ipod touches, iphones and laptops dynamic.
    it seems the router companies are now allowing users to have DHCP networks with reserved IP addresses based on the MAC address of the device which is very convenient. The linksys and airport extreme offer this feature.
    took about 5 mintues to set up all the devices.
  5. MikhailT macrumors 601

    Nov 12, 2007
    Of course it is possible as long as they are not in the same network. ;) For example, I can totally have your IP Address but I can't be connected to the Internet as you and I will be in the same network (Internet).

    Also external IP address isn't the same as internal IP address. Your network can have one single external (or multiple) IP address but hundreds of thousands of computers in that network can respond to the external network with the same IP address but each of them have their own IP address which is internal. (Go wiki on Network Address Translation or NAT to understand how it works in details)

    You can have two local computers with locally set to same IP but the computers will start to complain due to massive packet interferences in the network, Windows will alert you of that fact.

    DHCP will try its best not to assign same IP addresses to the same computer in the same network but sometime there is a lag that could occur with two computers with same IP address but often enough they are resolved on their own.

    Can you share your IP addresses (don't share the last two digit, make it up because otherwise people can try to DoS or hack into your machine)? I doubt that you have same ip address for those two computers otherwise you'll be connecting to your own computer.
  6. Not Available thread starter Guest

    Jun 30, 2009
    Well here's the email I've sent from the PC machine to my GMail, containing all the information taken from the Windows' network details menu:
    And here's what I have from "Network" in OS X's System Preferences:

    Attached Files:

  7. r.j.s Moderator emeritus


    Mar 7, 2007
    192.168.x.x are private addresses, two computers on different networks can have the same private address because it doesn't mean anything beyond the router/cable modem.

    Google NAT (Network Address Translation) for more info.
  8. MikhailT macrumors 601

    Nov 12, 2007
    You're using the internal IP address that I was talking about, they are not part of the global Internet network. You are getting an internal ip address assigned by DHCP server inside your modem. It is not the same network as the other location, the other location is a different internal private network that has it own 192.x.x.x address space.

    Two modems, two private internal networks, both PCs can have the same IP address because they are not in the same network.
  9. crewrules101 macrumors member

    Aug 9, 2007
    OP, refer to my previous post.

    To check your actuall IP address that is connected to the internet (your external IP address) go to

    Using the Run command on a PC and typing in the ipconfig is just showing your local address. The same applys to when you are looking at the networking preferences in System Preferences on a mac.

    If you need more help, feel free to PM me, and i will explain more.

  10. Not Available thread starter Guest

    Jun 30, 2009
    I'm not that free, apparently I get an error message about you not being able to receive PMs from other members or something.

    Oh, so is there a way I can see the actual IP address from System Preferences/Control Panel, or would it help if I wrote a PHP script to always have with me when I need the real address?
  11. yg17 macrumors G5


    Aug 1, 2004
    St. Louis, MO
    No, System Prefs won't show you your external IP
  12. jzuena macrumors 6502a


    Feb 21, 2007
    Lexington, MA, USA
    You could get a Dashboard widget like iStat pro. It will show both your local and global IP address. Or you could go to a web site that echos back the address you are connecting from. This will always be your global address. If you don't like the ipchicken suggestion (and how could you not like a website with a name like that :cool:), there are others: just google "my global ip address" and pick one of them.
  13. Not Available thread starter Guest

    Jun 30, 2009
    Yes, IPChicken is great! :) I've used it, now I've got both addresses.

    I'll also look into iStat. I'd say it's handier.

    Thank you all!

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