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quick question??

Discussion in 'General Cisco Certifications' started by Beany, Nov 11, 2010.

  1. Beany

    Beany Bit Poster

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    afternoon,

    CCNA book states that when two devices receive and transmit data on the same pins, a cross over cable is required..

    so a PC connected to a router will require a cross over..

    but from my experience, when ever ive set up a router connecting to a PC, i cant remember using a crossover cable... things work...

    why does the book state a cross over cable is needed?

    thanks
     
  2. gosh1976

    gosh1976 Kilobyte Poster

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    Is it a home or small business router from an ISP? If so those are really router, switch, and sometime WAP combination devices so you are really plugging in to what amounts to a switch port.

    Cisco also has WIC cards for routers that are like little switches. So you could be plugging in to something like this: http://www.cisco.com/en/US/products/hw/routers/ps221/products_data_sheet09186a00801c749d.html


    Oh and just to confuse the cabling a bit more for the real world don't forget about the MIDX auto command for interfaces on switches which is used to enable automatic media-dependent interface with crossover detection.
     
    Last edited: Nov 11, 2010
    Certifications: A+, Net+, MCDST, CCENT, MCTS: Win 7 Configuring, CCNA
  3. Theprof

    Theprof Petabyte Poster Forum Leader

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    It's because a lot of NIC's have the functions of a crossover cable built in, which is why it's not always required. A crossover cable has receiving and transmitting functionality on both ends which allows it to transmit full data between ethernet devices.
     
    Certifications: A+ | CCA | CCAA | Network+ | MCDST | MCSA | MCP (270, 271, 272, 290, 291) | MCTS (70-662, 70-663) | MCITP:EMA | VCA-DCV/Cloud/WM | VTSP | VCP5-DT | VCP5-DCV
    WIP: VCAP5-DCA/DCD | EMCCA
  4. gosh1976

    gosh1976 Kilobyte Poster

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    I didn't realize that many NICs had that capability. A quick google search shows quite a few network cards with Auto-MDIX. The simplest solution or answer is usually the best!!
     
    Certifications: A+, Net+, MCDST, CCENT, MCTS: Win 7 Configuring, CCNA
  5. cajensen

    cajensen Bit Poster

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    Just remember that you are studying for the CCNA which I do not think take those into consideration.
     
    Certifications: CCNA, A+, MCTS 70-642, Security +
  6. soundian

    soundian Gigabyte Poster

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    That's the key to that sentence. Not all devices RX/TX on the same pins. I would imagine the majority of devices designed to have NICs plugged in to them would have the pins crossed-over internally.
     
    Certifications: A+, N+,MCDST,MCTS(680), MCP(270, 271, 272), ITILv3F, CCENT
    WIP: Knuckling down at my new job

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