Straight-through
cables get their name from how they are made. Out of the 8 pins that exist on
both ends of an Ethernet cable, each pin connects to the same pin on the
opposite side. Review the diagram below for a visual example.
Notice how each wire corresponds to
the same pin. This kind of wiring diagram is part of the 568A standard. The
568B standard achieves the same thing, but through different wiring. It is
generally accepted to use the 568A standard as pictured, since it allows
compatibility with certain telephone hardware- while 568B doesn’t.
Straight-through cables are
primarily used for connecting unlike devices. A straight-through cable is typically used in the
following situations.
- 1. Connecting a router to a hub (but not in up-link port of hub).
- 2. Connecting a computer to a switch
- 3. Connecting a LAN port to a switch, hub, or computer.
Note that some devices such as
routers will have advanced circuitry, which enables them to use both crossover
and straight-through cables. In general, however, straight-through cables will
not connect a computer and router because they are not “unlike devices.
In a straight through cable, pins on one end
correspond exactly to the corresponding pins on the other end (pin 1 to pin 1,
pin 2 to pin 2, etc.). Using the same wiring (a given color wire connects to a
given number pin, the same at both ends) at each end yields a straight through
cable.
