Network Troubleshooting Tools – CompTIA A+ 220-901 – 4.4

You’ll need the right tools to properly troubleshoot a network. In this video, you’ll learn about troubleshooting with cable testers, loopback plugs, punch-down tools, toner probes, cable crimpers, and wireless locators.

<< Previous: Troubleshooting NetworksNext: Network Troubleshooting at the Command Line >>

If you’re trying to resolve problems on a network, then you’ll need to have the right tools in your bag. In this video, we’ll go through some of the most popular network troubleshooting tools.

A simple, and relatively inexpensive, tool to have in your tool bag is a cable tester. This is something that’s going to provide you with a continuity check from one end of a cable to the other. It can identify when there might be pins missing between both sides of the cable. Or maybe times that you’ve accidentally crossed the wires when you’re crimping down those connectors.

You don’t generally use cable testers for more advanced functions, like identifying the amount of cross talk on a cable, or the amount of signal loss from one end to the other. For those, you’ll need a more advanced, and more expensive, cable analyzer.

Here’s an example of a cable tester. You can see that you have the tester on one side, and then you have a probe that you put on the other side. This is able to determine exactly what pins are matching up on both sides of the cable.

Another nice tool to have available is a loopback plug. This is a tool that you’ll use to take everything that’s being sent out of the physical interface and have it turn around and go right back into the receive interface on that device. If you’re testing a physical port, you’re going to need a loopback plug. There’s loopback plugs for serial ports. You might also see these referred to as RS-232 interfaces. And they might be 9 pin or 25 pin loopback plugs.

I have many loopback plugs I use for my network, whether I’m running ethernet, or T1, or fiber connectors. One thing to keep in mind is that these loopback plugs are not cross-over cables. A cross-over cable is used to connect two devices directly to each other. A loopback plug is used only to test the physical interface on one device.

With loopback plugs, you never use these until there’s a problem or you need to perform diagnostics on a particular physical interface. You want to have loopback plugs available for all of your different interfaces. So make sure that you’ve collected together the ones you would use for your fiber connections, your ethernet connections, and so on. You might also want to consider making your own loopback cable, similar to the one that I created right here. There’s a page that will show you how to create loopback plugs, ethernet cables, crossover, modem cables, null modem, and more at

If you’re going to work with punch down blocks, such as 66 blocks, or 110 blocks, then you’re going to need a punch down tool like this one. This is going to push the wire into the punch down block, cutting through the insulation, and making a solid connection to the copper wire underneath.

This can also be tedious process as you connect a wire, after wire, after wire to these punch down blocks. But it’s one of the best ways to connect a permanent link for your wires in your network. This is also going to trim the wires as you’re punching it down, making a very neat connection on the punch down block.

Here’s a 110 block punch down. You can see that organizing these wires together is very important. You need to know exactly where you’re connecting these wires and where that cable is leading. You also want make sure you maintain the twists when you’re punching it down into the block. You can see here this person did a very good job of maintaining the twists all the way up until the very last point where it had to make the connection to the punch down block.

There are so many different wires and connections when you’re working with these punch down blocks that you want to be sure to follow best practices for documentation. Make sure you write down all of the different connections and where they’re going. You might want to tag certain cables, and label them with where they might be going. Or, you might want to write directly on the board that is used to mount all of these punch down blocks. So that you always know where these wires are going.

If you are working on a network that does not have the proper amount of documentation, you might want to get a toner probe. This is going to help you identify where the two different ends of a cable might be. This consists of a tone generator that is putting a sound on the wire. You can see the generator here. And also an inductive probe. This doesn’t have to physically touch the copper, it just has to get close. It has a small speaker on it, so that you’re able to hear the sound that’s being created by the tone generator on the other side.

To trace these wires back, we want to connect the tone generator directly to the wire. There might be alligator clips on the tone generator. Or there might be RJ45 connectors which makes it very easy to connect to a modular jack. You then use the probe to go to where you think the other end of the wire might be. It’s usually easier to put the tone generator out where the user’s workstation is, and then use the inductive probe on your large wall of punch down blocks.

If you’re going to run your own network cables, then you’ll want to have a good cable crimper. This is going to pinch the connector onto the end of each one of these cables once you’ve run it from one side to the other. This is usually the last step in the process, and sometimes the most important one. Because if you get the wires wrong in that connector, you’ll need to cut it off and try crimping it again.

The crimper itself is taking the metal prongs that are inside of that modular connector and pushing them through the insulation that’s in those copper wires. If you were to look very closely at these modular connectors before they’re crimped, you can see they are sticking up just a little bit. It’s the crimper that pushes these down and makes a solid connection onto the cable itself. You can see here that the tongs are pushed into the copper wire, making a solid connection and a good crimp.

The crimper also pushed in this connector on the back of the connector so that it holds the cable in place as well. So that it won’t pull out from all of the work you did putting those wires in the modular connector.

To make your own cables, you want to make sure, of course, you have a very good set of crimpers. Make sure you have also a good set of electrician scissors. These are shorter scissors that are able to have much more control over where you’re cutting. You also might want to get a wire stripper as well.

The modular connectors that you’re going to use inside of your crimper should also match the type of wiring that you’re using. Different categories of cable are going to use different types of connectors. They all look very similar but there are minor differences between the different categories of modular connectors.

And, of course, you’ll need to practice this. You’re not going to get it right the first time. These are very small wires in a very small connection. But after a while, you get the hang of it and you’re able to create your own cabling very easily, and very quickly. And you can customize exactly where your wires are going to go.

Another nice tool to have in your bag is one that can locate wireless networks. This might be software that you’re loading on a laptop, or mobile device. Or it might be a custom built piece of hardware designed to find wireless networks. This should not only identify where the networks are, it should show you configuration information, show you signal information, identify what frequencies are in use, and much more.