Cisco CCENT / CCNA Certification Exam Tutorial: Crossover, Straightthrough, and Rollover Cables

To pass the Cisco CCENT and CCNA certification exams, you have to know what cable type is appropriate for a given situation. It’s also a good idea to know this for working in real-world production networks as well! After all, if we have the wrong cable, we don’t have a network!

This is particularly true of the following scenario, where we have:

A laptop connected to a switch (Cable 3)

Two switches connected to each other (Cable 2)

A PC connected to a switch (Cable 1)

This is a very basic and common topology, but we’ve got three different cable types in there! Working from top to bottom, let’s take a look at the different cables we’ll need to make this work.

For Cable 1, we need a straightthrough cable. A straightthrough cable is used to connect a PC to a switch or hub. In a straightthrough cable, the wire connected to Pin 1 on one side is connected to Pin 1 on the other, the wire connected to Pin 2 on one side is connected to Pin 2 on the other, and so forth.

It’s very common to connect two switches to allow them to send data over that connection, and the connection between two switches is called a trunk. You’ll learn all about the particulars of trunking in your CCNA studies, but the first thing we have to do is make sure we have the correct cable!

To allow two switches to communicate with each other, a special cable type is needed. Regular straight-through cables will not allow two switches to form a trunk.

What we need is a crossover cable. The wire connected to Pin 1 on one side will no longer be connected to Pin 1 on the other, as it was in a straight-through cable.Four wires will “cross over” in a crossover cable: