There are many tools in the network administrator’s arsenal. In this video, you’ll learn about crimpers, punch-down tools, loopback plugs, fusion splicers, and much more.
If you’re going to be working on an ethernet network, then you need to have a good set of crimpers in your toolbox. Crimpers provide the tool that will allow you to fasten an RJ45 connector onto the end of an ethernet cable. There are also crimpers available for fiber, coax connections, and other types of media as well. But we most commonly see this used in untwisted pair cabling.
This is usually the last step of the process. You’ve already run a cable through the ceiling or through the walls. And now you need to fasten an RJ45 connector to the end. There are metal prongs inside of the RJ45 connector that are pushed through the insulation and make contact with the copper that’s on the inside. It’s the crimper that pushes those metal prongs into the RJ45 connector.
Here’s a picture of an RJ45 connector before doing the crimping. You can see that the copper connectors are pushed out just a little bit on the empty RJ45 connector. We’ll put the cable inside of this connector. The crimper will push down on all of these connectors. And you can see there are pointy connections here at the bottom that push into the insulation and make contact with the copper inside.
Here’s a view of the cable after the crimp has been made. Not only have you pushed the wires through, and you can see now that copper connector has been pushed into the wire itself. And the crimper also pushes through a piece of plastic that helps to hold the cable in place.
If you’re going to be crimping some ethernet cables, you will, of course, need a good pair of ethernet crimpers. And you’ll also want a good pair of electrician’s scissors. Sometimes you’ll see these referred to as cable snips. There are also wire strippers that can be used to quickly remove the outside sheath of the cable, making it a little bit easier to untwist and insert those cables into the RJ45 connector.
There are, of course, different cable categories. And you want to be sure that you’re using the appropriate RJ45 connector for the type of cable that you’re using.
It could be a bit of an involved process the first time you try to crimp an RJ45 connector onto a cable. You have to strip the cable, pull the wires out, make sure they’re in the right order, put them inside of the RJ45 connector, and finally crimp that down. So it does take a bit of practice to become proficient. But once you’re able to do this a number of times, you’ll have the skills needed to be able to create any type of ethernet cable you’d like of any length.
If you’re working inside of a data center or inside of a wiring closet, you may not be crimping the end of the cable onto an RJ45 connector. Instead, you may be fastening it to a punch-down block like the ones we have here. To be able to fasten those wires inside of the block, you will need a punch-down tool. There are different tools depending on the block that you’re using. So if you’re using a 66 block, you’ll need a tool specifically designed for that block type.
This is usually a bit of a tedious process. You have to put all of the wires into all of the empty slots and then punch down every single one of them. But these are not usually wires that will be moved. Once you punch them down into the punch-down block, they’re usually there permanently.
Not only is this punch-down tool fastening that wire into the punch-down block itself, but it’s also cutting off any excess wire that may be hanging out on the side, making it a very clean and very easy to manage installation.
If you are in the process of punching down a number of these connections, you may have tens, hundreds, or even thousands of these wires to punch down. So having them organized in your wiring closet is very important. You want to be sure that you’ve numbered each one of these connectors and that they correspond to the numbers that are in your punch-down block.
You also want to be sure to maintain the twists as close as possible to this punch-down block. You can see in this example, only a small amount of non-twisted wire is seen on the outside of this cable. Most of the twists have been maintained so that you have twist going all the way into the punch-down block.
And once these wires are punched down, you want to be sure that you document everything. This wire is probably coming from a desk that’s out on the floor. And you want to associate the jack number on the desk with the number associated with the punch-down block. This makes it easy to see the number that’s associated with an ethernet jack at someone’s desk. You can look at your documentation and tell very quickly where that may be connected on your punch-down block.
Unfortunately, we don’t always do the best job with our documentation. So it’s good to have some other tools that can help you identify where the end of a cable might be, especially if that cable is extended over a very long distance. To be able to do that, we need to use a tone generator, which is used to put a sound on the wire itself. And then we’ll use an inductive probe on the other end to find where that wire might be in this large number of wires that’s in our data center.
One advantage of the probe is that it’s inductive. You don’t have to touch the copper itself to be able to easily find where that wire might be. This is a very easy tool to use. And it can save you hours of time if you’re trying to find exactly the right cable. You would first connect the tone generator to one end of the wire. This might be in a modular jack underneath someone’s desk. It might be the end of a coax cable. Or it might be with punch-down connectors on a punch-down block.
You would then take the inductive probe to the other end of where you think that wire might be. And you would simply move it between all the wires to try to find where that signal is making noise.
Let’s think about a scenario where you might have hundreds or even thousands of wires coming in from the ceiling, and you’re just trying to find the one wire that’s connected back to a user’s desk. So you’ll go back to that user’s desk, place the tone generator on the jack on their desk. And then you have hundreds of wires inside of your data center to go through.
In this example, we’re just going to go through four wires. But I’m going to show you how fast it is to be able to do this. I have my inductive probe. I’m going to push down on this inductive probe and simply touch it to every cable that I happen to have in this list. And when I get to the right cable–
[ELECTRONIC BEEPING]
–you can see that it turns on with the light. It makes a noise. And I have identified where the end of that cable happens to be on the other side.
You might be working with a switch, a router, a firewall or some other device where you’re concerned about the number of errors that you’re seeing on a particular interface, but you’re not quite sure whether the problem is with the cable connected to that interface or if the problem is with the hardware of the interface itself.
One thing that can help you with your troubleshooting is to use a loopback plug. This is perfect for testing physical ports because it takes signal that is coming into that loopback plug, simply turns it around, and puts it right back into the device where that signal was originally sent. This can be seen over serial connections on nine-pin or 25-pin RS-232, maybe a network connection, such as an ethernet or a T1. And there are fiber loopbacks that you could use over fiber connections as well.
These are not crossover cables. You are not connecting two devices with a loopback plug. You’re instead coming out of one device and simply looping back directly into that same device. You would then send a data stream outside of that device.
That data stream will obviously be looped back to the receive ports of that device. And you can examine the received data stream to see if it matches what you’ve sent on the transmit data stream. If both of those are matching, then you can feel pretty good that interface is working properly. But if you find that you still have errors on this connection, it could be that your transmit or receive circuitry has some type of hardware problem on that device.
If you need to perform detailed troubleshooting of a copper or fiber network drop, then you may want to use a TDR or an OTDR. TDR is time domain reflectometer, used for copper connections, and the optical time domain reflectometer is used for fiber. These devices can provide you with a lot of troubleshooting information. They can estimate the entire cable length so you have an idea of exactly how far that drop might go. You can see if there are any splices in this cable. And it tells you exactly how many feet down that particular splice might be.
You can see the impedance of the cable. You can see what the signal losses might be. And it’s a great way to certify that a particular cable installation was done properly.
There’s sometimes a single button or an option to automatically test that link to be able to see what type of signal would be supported over that connection. And if you do happen to have a break in the fiber or the copper, a TDR or an OTDR can find that break very quickly.
The TDR works by sending an electrical pulse down the cable and then listening to see if anything is reflected back to the TDR. If there’s a problem with that cable, a break in the wire, or any difference in the impedance of that copper, a reflection will be sent back to the TDR. The TDR then performed some calculations based on how long it took to receive that reflection and can tell you how far down that cable the problem happens to be.
An OTDR effectively does the same thing over a fiber connection, but it does it with the reflection of light. Here’s a visual of how this particular reflection works. You can see there is a problem with this cable. And as that signal is sent through, some of that signal is sent back to the TDR as a reflection.
Let’s see that again. We’ll send the signal. The signal finds the flaw in the cable, and there’s the reflection being sent back to the TDR.
These tools can be relatively expensive, especially if you’re getting a fiber TDR or OTDR. This means that you’ll want to have some additional training so that when you receive this TDR, you’re able to use all of the different features of this very complex product.
Once you become familiar with the operation of the product, you’ll find that it is a very quick way to find problems with layer one, or the physical layer, of your OSI model. And if you ever have a cable installation that you want to certify for running 100-megabit, gigabit, or even 10-gigabit ethernet, you can use the TDR to provide that certification.
Another useful tool, and one you certainly should have in your toolbox, is a multimeter. One common use for a multimeter is to provide AC voltage measurements. You can plug into your wall outlet and be able to see if you’re getting 110 or to 220-type voltage from that connection.
You can also check DC voltage, which is especially useful inside of your computers, or if you’re trying to check the voltage that’s coming from a power supply. This is also good for checking batteries. So you can see if the CMOS battery on your motherboard has the voltage it needs to be able to operate properly.
And the multimeter can be used for continuity checks. You can use one probe of the multimeter on one side of a wire, put the other probe on the other side of the wire. And if the multimeter beeps, then you have continuity all the way through that cable.
You can use this feature to determine cable connectivity. You can check the fuses of devices inside of your components. Or you can use it to create a wire map if you have access to both sides of the cable.
If you don’t need some of the capabilities of a multimeter and all you really need is a wire map, then you might want to get a cable tester. With a cable tester, you simply plug the two sides of your cable tester into a wire. And it will very quickly show you what the wire map might be. If you need to confirm that pin one is connected to pin one and pin two is connected to pin two, this is the device that does this very quickly.
And of course, it can also tell you if you happen to mix any of those wires with your crimps. This obviously doesn’t have a lot of advanced capabilities. It’s really designed just to show you if the pins are connected to each other. If you need more advanced capabilities like identifying bad cables or identifying where there might be crosstalk or signal loss, you might need to get a TDR.
Another great tool for your toolbox is a tap or a port mirror. You could use a physical tap, where you are physically disconnecting a wire, putting this tap in the middle of this connection, and then plugging your monitoring tools into the tap to receive the copy of the data. If you’re plugging in a physical tap and it doesn’t require any type of power, then you’re using a passive tap. If your tap requires a power source to be able to perform that tapping function, then you’re using an active tap.
You may find that you have a port mirroring capability built into your switch. This may be called a port redirection, or in the case of Cisco, you’ll see this called a SPAN, which stands for switched port analyzer. This is software-based, which means you configure the switch to take data from one interface and copy it to a separate port on the switch. This usually has limitations as to the type of data that can be sent, the amount of data that can be moved to a particular interface, and how many of these tapped connections you can use. But if all you need is a way to quickly grab some packets so that you can do a quick analysis, you may be able to do that with the port mirroring capability in your switch.
This is the image that’s on a DS3 tap. You can see that you have six different connections at the top of this tap. Normally, you would have two devices, a DTE device and a DCE device, where the transmit and receive simply connect to each other. When we put the tap in the middle, we’re simply completing through the tap going one direction and completing through the other direction. When that information is moved through the tap, a copy is sent to the monitoring ports on the tap. And then you can connect to your network analysis tool to be able to view all of the traffic between those two devices.
If you’re working with a fiber connection, then you’ll need some additional equipment to help you with your troubleshooting process. One tool that becomes very useful is a fusion splicer, which allows you to connect two ends of a piece of fiber together. This is a very precise tool that allows you to connect those fibers together with a minimum of light loss and very little reflection.
If you need to create your own connectors on a fiber, you can use the fusion splicer to be able to connect those properly. Or maybe you need to extend the length or remove a section of fiber. And you can use the fusion splicer to be able to make those changes.
The fusion splicer uses heat to be able to connect those two ends of the fiber together. And once that’s done, it is just as strong as the original fiber. As you might expect, this does involve quite a bit of training to become very good at using the splicers. And of course, you’ll need the very expensive fusion splicer to be able to perform this function.
Here’s a better shot of this fusion splicer. You can see the fiber is coming in from both sides. You have this protective sheath around the fiber. When that’s removed, you can see that inside of this are the very small pieces of fiber. And they’re going to connect together right in the middle in this fusion splicer to be able to make that connection.
Once you have fused that fiber together, you may want to run some tests to make sure that the maximum amount of light is going through that connection. And you can use a light meter to be able to see just how much light is being received on the other side. You would send a laser or LED light through one end of the device. And on the other end, there would be a measurement tool telling you exactly how much of that signal made it through. These can also be used when you’re installing fiber equipment to ensure that you’re receiving enough light for that device to use.
Another challenge we have when installing wireless networks is making sure that the frequencies that we’re using are not being used by other devices and therefore creating interference that could slow down our network. In order to see just what frequencies may be available, we might want to use a spectrum analyzer to be able to see what the entire spectrum might be doing.
This can solve some significant problems, especially if users may be having disconnections or slow file transfers. You can really see exactly what may be communicating on the frequencies near your area. If you use the spectrum analyzer and you see that there is a lot of activity over a number of frequencies that you’d like to use, you might want to change the configurations of your devices to use some frequencies that may not be in use.