Why does my one PC require a crossover cable for the router?

Discussion in 'Computing and Networks' started by spinnaker, Feb 20, 2010.

  1. spinnaker

    Thread Starter AAC Fanatic!

    Oct 29, 2009
    4,887
    1,015
    I just noticed my one PC has a crossover cable to connect to the router. If I use a straight trough patch cable it does not work.

    This is a newer PC with a Biostar MOBO and a AMD Athlon II on board.

    I have an older PC that uses the straight through patch cable


    Here is where it gets really strange.

    If I connect the patch cable direct between the old PC and the new PC it works!!!


    I would think I would have needed a straight cable since I need a crossover for the router. Any idea why this is??
     
  2. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
    some newer PC's can detect the polarity of the data lines on the Ethernet cable so no need for a crossover cable (but this depends on the ethernet controller they have installed on the mobo..... but some older routers needed a crossover to connect to another router and to a PC..... I keep a handful of both types of cables around, because you never know which one you need....
     
  3. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    Routers that required a crossover connection usually have one port dedicated for this and the rest use straight wired. Sometimes this port is switchable between the two modes. Sometimes it is called uplink or something like that.
     
  4. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
  5. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234

    For 8 dollars, I can get 2 of each cables (2 Xovers, 2 patch), cables are cheaper than adapters......

    My .02
     
  6. spinnaker

    Thread Starter AAC Fanatic!

    Oct 29, 2009
    4,887
    1,015

    That is kind of what I figured. But it does not work with the straight cable. I would think it worked with both.


    But I can not say for sure if I shut everything down after swapping cables. Maybe I need to do that for it to sense the new polarity.

    I'll give that a try.


    It is a very old router BTW. Still works ok. :)
     
  7. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    But the implications of what I said are that it depends upon which socket you plug into in your very old router.

    For instance if there is only one uplink port, you cannot plug both pc connections into it.
     
  8. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    ...But you don't look as cool as you would with a crossover keychain.:cool: Duh. Fashion met function.
     
  9. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234

    my bad, I was never very good with making a good fashion statement :rolleyes:, I just thought the cables went with my blue and yellow pocket protector better, lol :D
     
  10. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234

    If only 1 uplink is available, you can connect another router to it using a crossover cable and just connecting to one of the other available ports... same setup I use to expand my routers available Ethernet connections, and to connect to my WiFi router which is in turn connected to my DSL modem (See orange xover cable in pics)......

    Router 1 xover.jpg

    Router 2 xover.jpg
     
  11. sbombs

    Member

    Feb 26, 2010
    33
    0
    It is possible that one of the ports has Auto-MDIX.

    Copypasta from the wiki http://en.wikipedia.org/wiki/Auto-MDIX

    Auto-MDIX (automatic medium-dependent interface crossover) is a computer networking technology that automatically detects the required cable connection type (straight-through or crossover) and configures the connection appropriately, thereby removing the need for crossover cables to interconnect switches or connecting PCs peer-to-peer. When it is enabled, either type of cable can be used and the interface automatically corrects any incorrect cabling. For Auto-MDIX to operate correctly, the speed on the interface and duplex setting must be set to "auto".

    Also see: http://www.hp.com/hpinfo/abouthp/iplicensing/automdix.html
     
  12. Zetrox2k

    New Member

    Apr 8, 2010
    7
    0
    Newer network conrollers have the ability to auto-detect the type of cable that is plugged in unlike some older ones. If you have an old network controller, just replace it if its bugging you, you can get one for about AU$10-AU$15
     
Loading...