Internet sharing kills internet

Discussion in 'Mac OS X Lion (10.7)' started by zorro23, Aug 31, 2011.

  1. zorro23 macrumors newbie

    Joined:
    Apr 13, 2010
    #1
    I got internet connection over cable modem which is connected to switch and switch is also connected with Mac and PC.

    ............[Internet]
    ..................|
    ........[Cable Modem]
    .................|
    ..........[S w i t c h]
    ............|..........|
    .........[Mac]....[PC]


    When I turn on internet sharing on Mac over LAN Ethernet I lose internet connection. Network Diagnostics shows Ethernet - green, Network Setings - green, ISP - green, Internet - red (failed), Server - red (failed).

    I can ping PC (192.168.2.2) and cable modem.

    Lion is freshly installed (I have tried 10.7 and 10.7.1).
    This was working without any problem in Leopard and Snow Leopard, but now it is broken in Lion.

    Anyone can help?
     
  2. MisterMe macrumors G4

    MisterMe

    Joined:
    Jul 17, 2002
    Location:
    USA
    #2
    Of course, connecting the two computers to your modem via a switch to your modem kills your connection on one of the computers. Two devices cannot share the same IP on your LAN. You need a router which will then allow both computers to have equal access to the Internet. You may also share your Mac's access. If you do this, then you must configure your PC to go through the Mac. This is not optimal because your PC will be dependent on your Mac.

    Get a router!
     
  3. boilingpoint macrumors member

    Joined:
    May 18, 2011
    #3
    Lion use 192.168.2.x ip range for internet sharing. I think your router use the same ip range(192.168.2.x) and conflict with the ip range of Lion internet sharing.

    However as you said, it works in 10.6 or earlier mac os x despite of the ip conflict. So I think it may be a bug in Lion.

    For this ip conflict, apple provide an option to change the default ip range in 10.5&6. But stupid apple forget to add the option to Lion.
    http://forums.macrumors.com/showthread.php?t=1165626&highlight=

    So, you should wait for the bug fix, or change the ip range of your route with another range than 192.168.2.x.
     
  4. zorro23 thread starter macrumors newbie

    Joined:
    Apr 13, 2010
    #4
    To Mister Me:
    I know that my cable modem can't share IP to two computers.
    How it works - modem will assign connection to just one computer. It will be the first one which is asking for IP from him via DHCP. After that modem is finished with address casting.
    In my case this was always been Mac. After that Mac is taking role of router because Internet sharing service is turned on, and all other computers which are turned on after that are getting IP address and internet connection from Mac (not modem).
    As I said it is working on 10.5 and 10.6.


    To boilingpoint:
    Same range (192.168.2.x) is used in Snow Leopard.
    I don't have router on my network. Mac (Internet sharing service) is taking role of router (just not in Lion).
     
  5. MisterMe macrumors G4

    MisterMe

    Joined:
    Jul 17, 2002
    Location:
    USA
    #5
    It sounds like you have just been "lucky." From my understanding of your setup, you have your PC set to receive its IP from [any] DHCP server [on your LAN]. You have been hoping that your Mac secured its IP address first. In that way, your PC would be forced to secure its IP address from the Mac. However, nothing in your setup prevents your PC from getting its IP address from the modem, which then locks-out your Mac.
     
  6. zorro23 thread starter macrumors newbie

    Joined:
    Apr 13, 2010
    #6
    I turn on PC rarely and Mac is always on, so I really don't have any trouble from fact that PC can "steal" IP from modem.
    What is interesting (from my experience) is that even when I turn off Mac and turn on PC, PC will not get IP from modem until I reset modem. I suppose that there is some kind of reserved time in modem (like few hours) and IP address is probably reserved for MAC (Media Access Control) address of network interface which first got IP from modem, so it will not search for another one until that time pass, even if that network interface is not currently present.

    My problem in Lion is that I lose internet connection even when Mac is alone on network and I turn on Internet sharing on. I know there is no point of turning on internet sharing if computer is alone in network, I just wanted to give you example of my problem.
     
  7. MisterMe macrumors G4

    MisterMe

    Joined:
    Jul 17, 2002
    Location:
    USA
    #7
    OK. Be hardheaded. I am personally opposed, but there is a proper way to share your Mac's connection. You have not been doing it properly, but you seem to have gotten away with it in the past. However, your past has caught-up with you. You may now do it correctly or continue to have problems. The choice is yours.
     

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