Crossover cable

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A crossover cable connects two devices of the same type, for example DTE-DTE or DCE-DCE, usually connected asymmetrically (DTE-DCE), by a modified cable called a crosslink.[1] Such distinction of devices was introduced by IBM.

The crossing wires in a cable or in a connector adaptor allows:

  • connecting two devices directly, output of one to input of the other,
  • letting two terminal (DTE) devices communicate without an interconnecting hub knot, i.e. PCs,
  • linking two or more hubs, switches or routers (DCE) together, possibly to work as one wider device.

Examples[edit]

Use crossover cables for the following connections: Switch to switch, Switch to hub, Hub to hub, Router to router, PC to PC, Router to PC.

Other technologies[edit]

Some connection standards use different balanced pairs to transmit data, so crossover cables for them have different configurations to swap the transmit and receive pairs:

  • Twisted pair Token ring uses T568B pairs 1 and 3 (the same as T568A pairs 1 and 2), so a crossover cable to connect two Token Ring interfaces must swap these pairs, connecting pins 4, 5, 3, and 6 to 3, 6, 4, and 5 respectively.
  • A T1 cable uses T568B pairs 1 and 2, so to connect two T1 CSU/DSU devices back-to-back requires a crossover cable that swaps these pairs. Specifically, pins 1, 2, 4, and 5 are connected to 4, 5, 1, and 2 respectively.
Two pairs crossed, two pairs uncrossed
T1 crossover
Pin Connection 1: T568A
RJ-45 TIA-568A Left.png
Connection 2: T568B
RJ-45 TIA-568B Right.png
Pins on plug face
pair color pair color
1 2 Pair 2 Tip
white/orange stripe
1 Pair 1 Ring
blue solid
Rj45plug-8p8c.png
2 2 Pair 2 Ring
orange solid
1 Pair 1 Tip
white/blue stripe
3 3 Pair 3 Tip
white/green stripe
3 Pair 3 Tip
white/green stripe
4 1 Pair 1 Ring
blue solid
2 Pair 2 Tip
white/orange stripe
5 1 Pair 1 Tip
white/blue stripe
2 Pair 2 Ring
orange solid
6 3 Pair 3 Ring
green solid
3 Pair 3 Ring
green solid
7 4 Pair 4 Tip
white/brown stripe
4 Pair 4 Tip
white/brown stripe
8 4 Pair 4 Ring
brown solid
4 Pair 4 Ring
brown solid
  • A 56K DDS cable uses T568B pairs 02 and 04, so a crossover cable for these devices swaps those pairs (pins 01, 02, 07, and 08 are connected to 07, 08, 01, and 02 respectively).

See also[edit]

References[edit]

  1. ^ Dean, Tamara (2010). Network+ Guide to Networks. Delmar. p. 657.