Network Tools – CompTIA A+ 220-1101 – 2.8

A good technician will have the right tool for any circumstance. In this video, you’ll learn about cable crimpers, WiFi analyzers, tone generators, cable testers, and more.

When are you running new cables, it’s very common to run the cable itself without any connectors on the end. So you need a tool that’s specially designed to add those connectors onto the end of the cable. We call these cable crimpers And they look very similar to a pair of pliers, but they’re actually very specially designed to add that connector onto the end of the cable. There are different types of shrimpers that you can use. And they’re designed to add a connector onto the end of coaxial cables, twisted pair cables, or fiber.

This is usually the final step in the process. You’ve already run the cable through the floor or the ceiling, and you have the cable on both sides that need to have a connector added to the end of those cables. For twisted pair cables, these crimpers are pushing prongs through the installation and into the copper in the wire itself. Here’s an RJ45 connector before it’s used inside of a crimper. The cable would obviously be put into the back of this RJ45 connector. And you can see the copper connections at the end of the RJ45 connection.

You can see the copper connection sitting just above the RJ45 connector here. And when you use the crimper, it pushes down all of those connectors into the wire. Where the wires are connecting, you can see these sharp prongs at the bottom that are pushed through the insulation to make a connection with the copper inside of each individual strand. This extends that copper inside of the wire into these copper connections which then connect to the device that you’re plugging into.

After making the crimp, you can see that those connectors have been pushed down into the RJ45 connector. And you can see where those spiky ends of that copper connector have now made a connection into the wires that are inside of that RJ45 connector. If we look at the bottom of this RJ45 connector, you can see the copper that is on the outside of this connection, and that’s the copper that will be used by the device we’re connecting to.

This particular image is a very good crimp. You can see that the cables run all the way to the top of the RJ45 connector. It looks like they all have made very good connection into the wires themselves. And there is a cable stay at the bottom of that connector that pushes into the sheath to help hold the entire cable in place. If you’re running your own cable, then you’ll need a crimper to be able to add that RJ45 connector onto the end of the ethernet cable. You might also want to get a good pair of electrician scissors. These are sometimes referred to as cable snips. And a nice wire stripper can be used to quickly remove the wiring sheath from the outside of the ethernet wires.

There are differences in wire types. So if you’re using category 5 versus category 6 or category 7 cable, then there will be different connectors for each of those cable types. You want to make sure you’re using exactly the right connector for the type of cable that you’re using. This takes a little bit of practice, but once you become accustomed to cutting the cable sheath, putting the wires into the RJ45 connector in the right order, and crimping them down, you’ll find that you’re able to make your own custom cables.

If you’re working with a wireless network, then you don’t have to spend a lot of time crimping cables. But you do have to spend time understanding all of the different frequencies that are in use on that wireless network. To be able to understand exactly what’s happening over the air, you might want to make use of a Wi-Fi analyzer. These are analyzers that listen to all of the signals on this wireless network. And they’re able to provide you with information about what frequencies are in use and which ones may be open.

This Wi-Fi analyzer might be software that you would add to a laptop or a mobile device, or it might be a purpose-built piece of hardware that’s specifically designed to analyze Wi-Fi networks. This can be very useful if you’re in an area with a lot of Wi-Fi access points, and allows you to see exactly where interference may be occurring on this network. Being able to visually see what’s happening on the network can also help you when you need to make changes. So if you need to adjust where a Wi-Fi antenna is pointing, you can make that change and visually see exactly what the effect of that change might be.

If you’ve ever worked in a data center or large network where there are hundreds of different cables and you just want to find one of those hundreds of cables, then you probably want to use a tone generator. Sometimes you’ll hear this referred to as a toner probe, which describes both of the components that you would use to be able to identify that cable. One of these is a tone generator that adds a signal onto the copper wire. The other is an inductive probe. This inductive probe doesn’t need to touch the copper that’s inside of that cable. You just need to get close to the cable so that you can hear the tone that’s being generated on the other end of the cable.

This allows you to easily find where a cable might be, especially in environments that have hundreds or even thousands of cables running across the data center. You would first connect the tone generator to one end of the wire. This could be done with a modular jack that’s on the tone generator, or you may have alligator clips or some other connection type to that cable. You would then go to the other end of where this cable is. It’s usually in a large bunch of cables. And you would use the inductive probe to move from cable to cable to identify exactly which cable contains that particular tone.

Let’s give this a try. I’ve connected a tone generator to one of these four ethernet cables. They all look very similar to each other. So we need to understand exactly which one is connected to that tone generator. So now let’s use our inductive probe to be able to find where that tone generator might be. I’ll push the button to turn on the inductive probe. And I’ll simply push it against the outside of this cable. You can see there’s no noise and no light when I push it against the first cable, the second cable, the third cable. And then finally, on the last cable we have a noise and a light that shows that that’s where the tone generator is connected.

In some environments you’re not connecting an RJ45 connector, you’re instead connecting to a punch down block. This is a punch down block. And you can see that you have a specialized tool that you would use to connect that wire into the punch down block permanently. This can be pretty tedious if you’re working with a lot of cables, because you’re taking each wire that’s inside of the cable, putting each of those wires into their own slot on the punch down block, and using the punch down tool to individually fasten those wires to the punch down block. When you’re using this punch down tool, it’s not only pushing the wire into the punch down block, but it’s cutting off any excess wire, making a neat connection to the block.

When you’re working with punch down blocks, you’re usually managing many different cables. So it’s important to have very good organization when you’re using these punch down blocks. There are usually numbers on each of these punch down blocks that you can keep track of exactly what cable is connected to what connection. Another important characteristic of ethernet is that we maintain the twist as long as we can through this cable. You can see that these cables do maintain a twist all the way into the punch down block. It’s also good to keep very good documentation. Each one of these punch down connectors has a number. And it’s useful to duplicate that number on the other end of the cable.

Another great tool to have in your tool bag is a cable tester. These usually come in two different units. And you plug each one of them into the two ends of the cable. They’ll then perform a continuity test, and tell you if pin 1 is connected to pin 1, pin 2 is connected to pin 2, and so on. Some cable testers can also tell you if you happen to miss any of these cables or not punch them down properly or they may be able to tell you if you crossed wires between different pins. These cable testers are relatively simplistic, and they don’t have a lot of advanced functionality. For example, a cable tester may not be able to tell you what the crosstalk values might be between these wires or how much signal loss occurs from one end of the cable to the other. For those types of measurements, you’ll need a more advanced tools such as a TDR or Time Domain Reflectometer.

When you’re troubleshooting, it’s useful to know if the problems you’re seeing are related to the cable or related to the interface on the device. One way that you could test the interface is through the use of a loopback plug. You would have data coming out of an interface, looping back around, and going right back into that same device. This allows you to send information out a serial port, receive that information immediately back in that serial port, and be able to compare those two values to see if they match. If they don’t match then it’s very possible you have a problem with that physical interface. There are also loopback cables that you can get for ethernet connections, T1 wide area network, or fiber connections.

These are not crossover cables, you can see that you’re not connecting multiple devices together, this is instead used to send data out one interface and directly back into the same interface. Crossover cables commonly connect two devices directly to each other, but a loopback plug is effectively connecting a device to itself.

When you’re troubleshooting a network, it’s sometimes useful to see the data that’s going over the wire itself. But having access to that data can be problematic. One way that you could see the data on that connection is with a physical network tap. This allows you to disconnect a link, put our physical tap in the middle, and take a copy of all of that data and send it to an analyzer. This might be a passive tap that doesn’t require fiber. We commonly see that with fiber taps. Or it might be an active tap that is able to tap copper connections but requires power to be able to do that.

If you don’t have a physical tap, you may be able to use a tapping function that’s built into your switch. This is called a port mirror or a SPAN. The SPAN is an abbreviation for Switched Port Analyzer. This is a function built into the switch that’s able to take data that’s going between different interfaces on the switch and send a copy of that data to a third interface that you can then connect to an analyzer. There are obviously resource limitations in the switch and bandwidth limitations on the interfaces themselves. But if you need something very simple that can be used temporarily, a switch port analyzer or port mirror is a perfect solution.

Looking closer at this physical tap, you can start to see how this tap operates based on the design that’s on the outside. Physically, you can see that we would break the connection between two devices and put this tap in the middle. And since we have another cable between those devices going the other direction, we would break that connection and put the tap between that one as well. Now that we’ve completed this circuit, everything continues to flow between these two devices, but the tap is going to create a copy of that data and send it out to additional interfaces on this tap. You can then plug in a protocol analyzer or any type of monitor to be able to see all of the traffic that’s traversing these two devices.