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Straight-Through and Cross-Over cables, Difference between Straight-Through and Cross-Over cables

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Straight-Through Cables

CAT 5 UTP cabling usually uses only four wires when sending and receiving information on the network. The four wires, which are used, are wires 1, 2, 3, and 6. When you configure the wire for the same pin at either end of the cable, this is known as a straight-through cable.

Straight-Through cabling

From the figure we can see that the wires 1 and 2 are used to transmit the data from the computer and 3 and 6 are used to receive data on the computer.  The transmit wire on the computer matches with the receive wire on the switch. For the transmission of data to take place, the transmit pins on the computer should match with the receive pins on the switch and the transmit pins on the switch should match to receive pins on the computer.  Here we can see that the pins 1, 2, 3 and 6 on the computer matches with pins 1, 2, 3 and 6 on the switch. Hence we use the term Straight-through.

Following image shows the wire/pin positions of a Straight-through Unshielded Twisted Pair cable, using TIA/EIA 568A standard.

Note that the white striped wires are used to connect positive pins and solid color wires are used to connect negetive pins.

Straight Through wires TIA-EIA 568A

Cross-Over Cables

If we want to connect two computers together with a straight-through cable, we can see that, the transmit pins will be connected to transmit pins and receive pins will be connected to receive pins. We will not be able to directly connect two computers or two switches together using straight through cables.

Cross-Over Cabling

To connect two computers together without using a switch (or two switches directly), we need a crossover cable by switching wires 1 and 2 with wires 3 and 6 at one end of the cable. If we shift the pins, we can make sure that the transmit pins on Computer A will match with the receive pins on Computer B and the transmit pins on Computer B will match with the receive pins on Computer A.

Following image shows the wire/pin positions Cross-over Unshielded Twisted Pair cable, using TIA/EIA 568A/568B standards.

Note that the white striped wires are used to connect positive pins and solid color wires are used to connect negetive pins.

Cross Over Wire Position

The following table illustrates the different types of twisted pair cable which must be used to connect different network infrastructure devices.

  Hub Switch Router Workstation
Hub Cross-over Cross-over Straight Straight
Switch Cross-over Cross-over Straight Straight
Router Straight Straight Cross-over Cross-over
Workstation Straight Straight Cross-over Cross-over

Straight-through and Crossover terms are not much relevant for new Switch models. New Cisco Switches are packed with a feature known as Automatic Medium-Dependent Interface crossover (Auto-MDIX).  Auto-MDIX watches for a wrong cable connection and automatically changes the pins to make the link work.   Meaning that, you can use either Straight-through or Crossover to connect any type of device for Auto-MDIX enabled new switch models.

Warning: The concept of Automatic Medium-Dependent Interface crossover (Auto-MDIX) is not applicable for CCNA or Network+ exams. Straight-through and Crossover terms are relevant for CCNA or Network+ exams. If you pick the wrong cable, you may lose your marks.

 

              Jajish Thomason Google+
Related Topics
Network Infrastructure Devices- What is a Hub? Network Infrastructure Devices- What are Bridges and Switchs? Network Infrastructure Devices - What is a Router? Common Network Cable types
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