Connecting Two Computers With A Crossover Cable

Most of my articles in this website are about Windows Networking / File Sharing, or about Internet Connectivity, and start by assuming that you have several computers, and a router / switch / hub connecting them. But what if you have just 2 computers, and just want to quickly move files between the two? Or maybe you want to setup Internet service, for the 2 computers, without using a router to share the service?

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Make The Right Decision
Start by asking yourself – what do you want to do – both now, and in the future? If you just want to immediately connect just these two computers, and quickly move files between the two, without Internet service, then this is the right start.

If your future might include Internet service, or if you might end up with a third computer, then you would really be better off using a router.

If you want to connect the two computers, and share Internet service, you can do that using a crossover cable. But know the issues before you start.

  • If the computer with Internet service has it thru a dedicated modem, either:
    • Internally installed.
    • Connected externally, but thru a serial cable.
    • Connected externally, but thru a USB cable.

    then using a crossover cable is a valid solution.

  • If the computer with Internet service has it thru an Ethernet connection, or thru WiFi, then this is not a valid solution. If the Ethernet or WiFi connection is on subnet 192.168.0/24, this will not work at all. In the latter case, you will have to connect both computers directly to the LAN with subnet 192.168.0/24.

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Use The Proper Equipment
The simplest solution, for networking just 2 computers, is to get an Ethernet crossover cable, and connect the two directly. A single crossover cable is the equivalent to getting a hub (or switch or router), and a pair of straight-thru patch cables.

Please use Ethernet, not USB, for connecting your computers. USB networking requires additional drivers, and adds to complexity of the network. Ethernet drivers are native in all modern operating systems.

Please use a Cross-over Ethernet cable. A Straight-Thru, aka Patch, cable may work for some newer systems, which can automatically sense the need for a cross-over. But a cross-over cable will work all of the time, when you need to connect two computers directly.

Patch cables may come in many colours and lengths; some computer stores will have dozens of choices to suit your cabling needs. Cross-Over cables, when you find them in the store, will be explicitly labeled “Crossover”, and will come in one colour (probably orange), and one length (probably 3 or 5 foot).

Please buy a properly made cross-over cable. If you’re a masochist, or extremely desperate, you may make your own from a pair of patch cables, properly spliced. But Ethernet cables, that support modern high speed networks, require precision in their construction. While I’m a fan of do-it-yourself activities (as in the reason for this website), I don’t recommend do-it-yourself Ethernet cabling, when you’re setting up a network. Buy a cable, unless you’re very experienced with networking and can easily recognise the possible problems.

Use the Device Manager in Windows, and test the network adapter in each computer. Connect your cross-over cable to the two network adapters.

Now, will you be setting up your network to Share Internet Service? Or just to share files, with No Internet Service?

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Setup The Network – No Internet
If you just have two computers, and no Internet service to either, run the Network Setup Wizard on each computer. Select the last option

This computer belongs to a network that does not have an Internet connection.

Having connected the two computers physically, and checked that you have no physical problems, you need to make the logical (TCP/IP) settings. If you have Windows XP, or other current operating systems on your computers, you’re in luck. Modern operating systems use a system called APIPA, and should be able to provide ip settings automatically, so the two computers will connect to each other. If you allow the two computers to dynamically assign addresses, APIPA should take care of this for you.

Be prepared to get an error message – Limited Or No Connectivity – if you use APIPA configuration.

NOTE: if one of your computers is NOT running Windows XP, you’ll have to set the IP address and subnet mask manually. Remember IP addresses have to be unique for IP addressing to work.

  • Run “ipconfig /all”, from a command window, on each APIPA compliant computer first.
  • Make a list of which addresses are automatically assigned.
  • Manually configure each non-APIPA compliant computer.
    • Set each computer up with a unique IP address, in the 169.254.x.x subnet (written as 169.254/16 in many cases).
      • Each computer gets a subnet mask of “255.255.0.0”.
      • Each computer gets an IP address of “169.254.x.x”, where the “x.x” MUST be different for each computer. Check your list of addresses assigned by APIPA!
      • Each value of “x” must fall between 1 and 255 (not including either 1 or 255).
    • You assign IP addresses in the TCP/IP Properties wizard, generally accessed from Start – Network Connections – Local Area Connection – Properties – Internet Protocol (TCP/IP) – Properties. Select “Use the following IP address”. Only worry about IP address and Subnet mask, the other settings are only useful if you have an outside connection. With locally connected computers, just IP address and Subnet mask are essential.

Having connected the two computers physically, and checked that you have no physical problems, next Verify The Network – make sure that it works properly.

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Setup The Network – With Internet
If you have two or more computers, with Internet service to one, and wish to share the service to the others, run the Network Setup Wizard, first, on the computer that has Internet service. Select the first option

This computer connects directly to the Internet. The other computers on my network connect to the Internet through this computer.

Next, indicate which network connection is to be used for sharing the Internet service.

Finally, run the Network Setup Wizard on the other computers, and select the second option

This computer connects to the Internet through another computer on my network or through a residential gateway.

Having connected the two computers physically, and checked that you have no physical problems, verify that the network works properly.

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Verify The Network
Please verify that you have connectivity between the computers first.

  • Run “ipconfig /all” on each computer, from a command window. Note the IP address and subnet mask for each network connection.
  • Make sure that you don’t have a bridge, on any computer, unintentionally.
  • Verify that all computers are on the same subnet.
    • If this is two computers without Internet service, each computer should have an address of 169.254.n.n, and a subnet mask of 255.255.0.0. This will indicate that each is on subnet 169.254/16.
    • If this is two, or more, computers sharing Internet service, the first computer (thru which the others will be getting Internet service) must have an address of 192.168.0.1, and a subnet mask of 255.255.255.0 (on the connection used for sharing the Internet service). All of the computers getting Internet service thru the first computer must have an address of 192.168.n.n, and a subnet mask of 255.255.255.0, and show both DHCP and Autoconfiguration Enabled = Yes.
  • From each computer, again in a command window, ping the other. If, for instance, the address on Computer B is “169.254.1.2”, open a command window on Computer A, and enter:

    ping 169.254.1.2

    If you get back a series of responses like

    Reply from 169.254.1.2: bytes=32 time
    then you are ready.

When you open Windows Explorer on each computer, and look in Network Neighborhood, you should see both computers. And when you open (doubleclick on) one entry, you should see the folders and files.

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Troubleshoot The Network, If Necessary
So what if it doesn’t work, per the basic testing above? Well, now you start troubleshooting, and in this order.

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