can't get LAN to work

Discussion in 'Networking and Computer Security' started by DaRuSsIaMaN, Sep 25, 2005.

  1. DaRuSsIaMaN

    DaRuSsIaMaN Geek Comrade

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    hey guys, me and my roommate are trying to connect my computer and his laptop together. We're not using a router, we just tried linking the 2 comps with one cable directly. But for some reason, when we plug it in, it still says network cable is unplugged. Any suggestions?
     
  2. pelvis_3

    pelvis_3 HWF Member For Life

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    Your gonna have to get a CAT 5 Crossover Cable!
    It's essentially the same as any other network cable ecept with some wires crossed!
    The 'network cable is unplugged' thing will go away upon succesful connection!
    Also don't forget to 'enable' the connection!
     
  3. Anti-Trend

    Anti-Trend Nonconformist Geek

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    Pelvis_3 is right, a normal patch cable wouldn't work, as the 'send' and 'receive' pairs would be the same on both ends... collision city. You need a crossover, which has the send/receive pairs swapped on either end so direct data transmission is possible.

    -AT
     
  4. DaRuSsIaMaN

    DaRuSsIaMaN Geek Comrade

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    Oh, okay, awesome. A cable won't be hard to get. But could you explain what you said right there a bit more, please?


    So what exactly are the send/receive "pairs"? And you say in an ordinary network cable they're the same at both ends? I don't get it ... why does that cause "collision"?
    And also, when you plug such an ordinary cable into a modem, you still send data back and forth between it, not just one way. So what's the problem with sending data back and forth between 2 comps?

    Thanks
     
  5. pelvis_3

    pelvis_3 HWF Member For Life

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    You can recognize a crossover cable by holding the transparent RJ45 connectors at each end next to each other. If the wires in the connector attach to different pins at either end of the cable, you have a cross over cable. Otherwise it's a straight through cable!

    If you use a straight through cable the network card gets confused on where the packets are being sent to and drops them!

    Check out the Color Codes .
    Modems work differently to computers and have a slighlty different language :)
     
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  6. Anti-Trend

    Anti-Trend Nonconformist Geek

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    Let me quote verbatim from our Networking FAQ:

    Q: What is a crossover cable? What are they used for?

    A: In network cabling, there is often more than one way to wire the connector jacks at the ends of the cable. For instance, with Cat5 cables, there are two which are commonly used: type A and type B. Type A cables place the green pair on the outer edge of the jack and the orange pair around the center. Type B is the opposite, with orange on the outside and green around the center pair. Normal patch cables utilize one standard or the other. A crossover cable uses a type A connector on one end of the cable and a type B on the other. The gist of it is that the pair of wires that send and the pair that recieve are opposite on each end so that both ends are not trying to send through the same pair. This configuration is typically used to directly connect network devices, such as PC to PC (with no hub/switch), router to switch, or switch to switch. Some modern switches and routers feature auto-negotiating ports, which sense if the connection needs to be a crossover and adjusts for this on the fly. However, many devices still require crossover cables in order to uplink to another device.
     
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  7. DaRuSsIaMaN

    DaRuSsIaMaN Geek Comrade

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    Aight, thanks guys! Didn't even know there was a FAQ here ...
     

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