The Difference Between Straight Through, Crossover, And Rollover Cables

Posted on June 7, 2010

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The Difference Between Straight Through, Crossover, And Rollover Cables

There are generally
three main types of networking cables: straight-through, crossover, and
rollover cables. Each cable type has a distinct use, and should not be
used in place of another. So how do you know which cable to use for
what you need?

The Purpose of Straight-Through Cables

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:

straight through cables

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:

Use a straight-through cable when:


  • 1. Connecting a router to a hub
  • 2. Connecting a computer to a swtich
  • 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.”

The Purpose of Crossover Cables

Crossover cables are very similar to straight-through
cables, except that they have pairs of wires that crisscross. This
allows for two devices to communicate at the same time. Unlike
straight-through cables, we use crossover cables to connect like
devices. A visual example can be seen below:

crossover cable

Notice how all we did was switch the orange-white and green-white
wires, and then the orange and green wires. This will enable like
devices to communicate. Crossover cables are typically used in the
following situations:

Use a crossover cable when:


  • 1. Connecting a computer to a router
  • 2. Connecting a computer to a computer
  • 3. Connecting a router to a router
  • 4. Connecting a switch to a switch
  • 5. Connecting a hub to a hub

While the rule of thumb is to use crossover cables with like
devices, some devices do not follow standards. Others provide support
for both types of cables. However, there is still something that both
crossover and straight-through cables can’t do.

The Purpose of Rollover Cables

Rollover cables, like other cabling types, got their name from how
they are wired. Rollover cables essentially have one end of the cable
wired exactly opposite from the other. This essentially “rolls over”
the wires- but why would we need to do such a thing? Rollover cables,
also called Yost cables, usually connect a device to a router or
switch’s console port. This allows a programmer to make a connection to
the router or switch, and program it as needed. A visual example can be
seen below:

rollover cable

Notice that each wire is simply “rolled over.” These types of cables
are generally not used very much, so are usually colored differently
from other types of cables.

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A patch cable (also called a straight through cable) is configured with
all 8 wires in the same order on both ends of the cable. There are two
standard wiring configurations used for patch cables. They are 568A and
568B. Either configuration can be used, so long as the same
configuration is used at both ends of the cable.

With 568A:
Pin 1 – White/Orange
Pin 2 – Orange White
Pin 3 – White/Green
Pin 4 – Blue/White
Pin 5 – White/Blue
Pin 6 – Green/White
Pin 7 – White/Brown
Pin 8 – Brown/White

With 568B:
Pin 1 – White/Green
Pin 2 – Green/White
Pin 3 – White/Orange
Pin 4 – Blue/White
Pin 5 – White/Blue
Pin 6 – Orange/White
Pin 7 – White/Brown
Pin 8 – Brown/White

A cross over cable is configured with 4 of the wires in the same order
on each end. The other four wires are crossed (hence the name). One end
gets wired with the 568A configuration, while the other gets wired with
the 568B configuration.

First End:
Pin 1 – White/Orange
Pin 2 – Orange White
Pin 3 – White/Green
Pin 4 – Blue/White
Pin 5 – White/Blue
Pin 6 – Green/White
Pin 7 – White/Brown
Pin 8 – Brown/White

Second End:
Pin 1 – White/Green
Pin 2 – Green/White
Pin 3 – White/Orange
Pin 4 – Blue/White
Pin 5 – White/Blue
Pin 6 – Orange/White
Pin 7 – White/Brown
Pin 8 – Brown/White

A rollover cable is wired with each pin on one end of the cable
connected to the reverse pin on the other end. So the cable on Pin 1 on
one end of the cable connects to Pin 8 at the other end, etc. Rollover
cables are used to connect the serial port of a computer to the serial
port of a network switch so that you can configure the network switch.
These cables are not used for network connectivity.

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