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Question about crossover and straight-through cables

Discussion in 'General Cisco Certifications' started by r.h.lee, Feb 26, 2007.

  1. r.h.lee

    r.h.lee Gigabyte Poster

    I understand that you use a crossover cable to connect one PC to another PC because the TX pair on one side becomes the RX pair on the other side, and vice versa. That way, the "mouth" of PC1 is talking directly to the "ear" of PC2 and the "mouth" of PC2 is talking directly to the "ear" of PC1.

    However, is the reason why you use a straight-through cable from PC to switch is that the PC will consistently TX from the PC to switch and consistently RX from the switch to the PC on the same pins/pairs and the switch does the internal electrical "crossovering" between the inbound port to the outbound port?

    PC1 connected to a bridge that is connected to PC2.
    • PC1 sends a signal to the bridge on pin 1 and 2 to the bridge's port 1.
    • bridge receives signal on pin 1 and 2 of port 1.
    • bridge makes a MAC address table determination to forward the frame to port 2.
    • bridge sends signal on pin 3 and 6 of port 2.
    • PC2 receives a signal from the bridge on pin 3 and 6
    Certifications: MCSE, MCP+I, MCP, CCNA, A+
  2. supag33k

    supag33k Kilobyte Poster

    correct - the switch does the cross over for you...

    Remember that the proper naming is DCE [usually but not always routers and switches] and DTE [terminals and pc's]

    DTE = Data Termination Equipment
    DCE = Data Channel Equipment

    A good general explanation is here...



    Certifications: MCSE (NT4/2000/2003/Messaging), MCDBA
    WIP: CCNA, MCTS SQL, Exchange & Security stuff

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