- To pass the 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:
Local Pin 1 crosses over to Remote Pin 3
Local Pin 2 crosses over to Remote Pin 6
Local Pin 3 crosses over to Remote Pin 1
Local Pin 6 crosses over to Remote Pin 2
With the proper combination of rollover, straightthrough, and crossover cables, you're on your way to total network connectivity
