Walk through topics that should be addressed when installing a wireless network and look at interference, layout, and quality of signal.
- Installing a wireless network from scratch can be a big job. So if you're gonna be doing this, well first of all, in all probability, I don't install my own wireless networks. I have enough understanding of it, that when I hire people to do it, I can give them good instruction, and I can help them get the job that I need done. So really, when you think about what CompTIA is trying to get at, I don't think it's trying to make you a wireless network installer, I think based on the questions we're seeing, they really want you to be somebody who can work with contractors who do this stuff, in order to get a job done.
So the first thing you're gonna need anytime you're installing a wireless network, is you need a plan. And by saying a plan, I'm talking about a floor plan. So to get us started here, I've got a very, very simple floor plan to get us going. So we've basically got eight offices with a big hallway. And this is my office, and we're going to set up a wireless network. Now, I've got some devices here. So I've got some dipoles here, and these are all WAPs, by the way. Some dipoles, I got some patches, and I've got some directionals.
They could be yagi, they could be parabolics, don't really care at this point in the game. What we're gonna be talking about is overall coverage. And we're going to assume this is a very large space here. So we're talking probably 500 feet across. So with that understanding in mind, let's talk about some of the things that are gonna happen here. We've got all kinds of walls in here. Walls can be made out of concrete, walls can be made out of glass, walls can be made out of metal. And depending on what type of walls you have, you can have a real problem. So there's a lot of environmental path considerations.
What's gonna keep my signal from getting from a WAP to a client anywhere, and back from the client to the WAP? So really, walls are gonna be the big issue here. Well, one other thing can come into play, and that's interference. So we've mentioned interference before, different radio sources, things like that, I'll talk about that, but also things like large electric motors, for example, strong heat sources can interfere with radio waves. But in a typical office environment, it's not like we're running large 3 phase, 220 electric motors.
Hopefully, those kind of motors are down in the HVAC in the basement or up in the roof. So we usually don't have to worry about that too much. We will discuss the idea of interference in a different way in just a moment, though. Let's just get things started here for fun. So if I've got a big WAP, they're not that big, folks, I'm trying to make them easier for you to see on the screen, so if I've got a big WAP over here, and I've got a client way over here, what in the environment can cause trouble? So we have interference, but the other one we're gonna have is reflection.
So as a radio wave if propagating down, I mean, some of the radio waves will come straight, but other ones, depending on the material, might bounce back and forth. So reflection can be an issue. Reflection could be a big issue, for example, if I've got somebody in this room, and this is a metal wall, in terms of metal, metal tends to reflect radio waves pretty strongly. The other one is refraction. Refraction is when it actually creates a bend. So if I've got somebody over here, we can actually use refraction sometimes where it bends the radio wave signal, and it can actually work in our benefit.
Glass is a famous source of refraction for radio waves. The next one is going to be absorption. Absorption is a real problem. Big, thick concrete walls, for example, will just suck up all your radio waves, and it can be very irritating. It simply eats them alive, and you don't have much luck with that. And the last one is really more of a distance issue. If we've got a big long run like this, the radio wave is going to weaken over time. That weakening is what we call attenuation.
And that's a big distance limitation and the different types of 802.11 have very specific distance limitations, and you have to work within those. If we're going too far, we have other options. We'll talk about that in this episode, as well. Alright. So the first thing we're gonna have to do here, is we're gonna have to go through what's known as a site survey. With a site survey, what I'm doing, is I am walking around within the area, this is a fairly small office, but if I was doing this for a campus, I would be going crazy right now.
As I walk around, and I like to use wifi analyzers that work really well on phones, and I'm just gonna be walking around and plotting. So literally, I'd be on this guy right here, plotting around and trying to find sources. Now, the tool I use is called Wifi Analyzer. So as you see as I'm running Wifi Analyzer right here, this is a free tool, it's a good one. A lot of people use this. So right now I'm looking in the 2.4 gigahertz band. This is a very, very busy band.
You can see that this is very noisy. Look at all these different systems on here. So this could be a real challenge for me. Now I'm gonna switch over to the 5 gigahertz band. Now the 5 gigahertz band isn't too terribly bad. These are very broad channels, but as we take a look, we'll let this populate up a little bit, these particular channels, so around 100, 102, 104, completely empty. And it's a little bit busy up on the higher end of the 5G scale, too.
So a quick analysis like this tells me a lot. On the 5Gs I've got plenty of space. I got wide open spaces that I can go ahead and easily take advantage of. Now granted, most 802.11 standards will automatically set themselves to this, but I can do some other things. Like, for example, on the 2.4 gigahertz band, I might wanna go ahead and play a little game and try to get in between say, channels, let's take a look at this one more time, say between channels one and six. I can see a little space in there.
Maybe I might try channel three or four. With the big kids world, what we do is if we we're to hire somebody to do this, not only would they go ahead and check for all these channels, but they would generate something called a heat map. So a heat map, basically, they triangulate all of the different sources and they place, using colors, the relative strength of other SSID signals. So I don't wanna mess this up, but let me just give you an example of a heat map right here. Heat maps are fantastic, because not only do they give you the strength, they actually give you a position in 2D space where the sources are actually coming from.
Okay, so a wifi analyzer does a great job with this, and actually for most small offices, the tool that comes with, well, it doesn't come with my phone, I had to download it from the Google Store, does a great job in terms of getting me the basic insight I need to know on the relative congestion of my network. Alright. Well, as we come through here, now the big issue's going to be antenna placement. Now there's a couple of things that I just wanna give you as general rules. If possible, anytime you have an outside wall where you don't want the signal to be out, but you want the signal to stay in, you're gonna wanna use a patch.
So in this particular case, I've got a patch that shooting out this direction. And I might wanna do something like this, as well. So in this particular case, depending on the 801.11 standards I have, for example, if I'm trying to shoot 802.11a, in this particular case, if this distance is more than about 50 feet, I'm not gonna do it. If I'm trying to run 802.11ac, I may only need two patches for the entire office.
The challenge is, and this is something we all go through when we're working with antenna placement in 802.11, is you've got to try a few different places. It's very common to just tentatively hang an antenna, just to see what it looks like, running around with the analyzer on your phone looking for dead spots. On a setup like this, depending on the 802.11 standard, I'd be worried about right here, I'd be worried about over here, and I might be worried about any place like this where I've got a number of walls that guys are trying to get through.
So that would be one thing to consider. Another option is to get rid of the patches altogether, and just go straight with a dipole. In this particular case, we're taking advantage of a highly centralize diploe to hit all this. And again, this is something that's fairly easy to test. I've done many a wireless network where I just lay a access point on a ladder, and I just wanna see how it's going. So possibly, if I have a shorter range, like an 802.11a, or maybe even something like 802.11g, I might wanna consider something like this.
The answer is is there is no right or wrong answer until you do a wifi analysis and look for dead spots. When we do these installations, we go crazy on this. One of the other problems that people run into is in their quest to avoid dead spots, they overpower this, they throw big gain antennas on there, and that's never a good idea. In these particular cases, you're gonna be throwing on, if you're not using the default antennas, which are probably around the same amount, you might be throwing on a three decibel to five decibel gain antenna to make sure you're getting the coverage that you want.
Now the last thing I wanna talk about when it comes to antenna placement is the use of highly directional antennas. I've seen this done. So we got one directional antenna shooting right in this particular situation, and I've got another one shooting left. I mean, there's no such thing as a left and right antenna, it's relative to this example here. I have seen people place yagis in extremely long, narrow places. And that's okay, but generally when we're talking about yagis, I don't even have another building to show you here, but I might be putting this out here to shoot it over to another building, and have another antenna, in this case, we'd be talking 10, 20, 30 decibel gains to get these guys shooting together to allow us to have good connectivity.
We'll just get this guy right here. There we go. Those are some pretty yagis we got there. The big measurement that we use more than anything else is we use what's known as signal-to-noise ratio. The signal-to-noise ratio is a relative gauge of strength. So while an antenna may be measured with gain, the actual receiving value that we get is SNR or signal-to-noise ratio. The stronger the signal, the more negative it tends to register.
So people are like, oh, so negative value. It's not really a negative value, it's just relative to the access point from wherever you happen to be. Now, the ultimate test of the pudding on anything like this is simply to have the users give things a try. It is unfortunate, but no uncommon to do one wireless setup, and find yourself in a situation where you might have to throw a little something else in. In that case, we have a entire class of devices known as wireless range extenders.
A wireless range extender is a self standing device. It isn't hooked via RJ45 to anything, usually. And it is a self standing device that acts as a wireless repeater to allow a signal that comes in, and I'm pointing at corners, 'cause that's such a common place to put them, and then we could actually act as a bridge from one SSID to bring it into the wireless repeater, which then makes a big strong signal to use. I am mentioning that because it's on the exam, but I will also tell you that in my experience, wireless range extenders like these, wireless range repeaters, same animal, are difficult to use and they are not reliable.
In my case, I'm gonna go ahead and I'm going to run a cable and get the wireless access point where it should be, or get the right kind of wireless access point to make sure that that hotspot's gone. Now there is one more type of wireless network. And it's relatively new, it's been around for a few years, called mesh. With a mesh network, I'm gonna cheat here for a minute, and I'm gonna turn these into mesh WAPS. Now these look like a regular wireless access point, sometimes they're small, sometimes they look like a soda can, but what makes mesh unique is that I might have, here I'll use one of these patches, I might have only one legitimate wireless access point that's actually screwed down with RJ45, connected to a wired network, with mesh networks, these devices are designed to talk to themselves.
They are absolutely incredible for getting rid of dead spots in offices, especially weird places, in manufacturing and such. You could throw these in a bathroom, you could throw these in a closet, and because this device here only has to be close enough to one of these devices to repeat signal, it takes the concept of what I feel a wireless range extender should be, and using its own topology, it can actually work really, really well. I've been playing with wireless networks using mesh just a little bit as of late, and I gotta tell you, I'm pretty impressed with the strength of it.
So these are just some ideas. On the actual exam itself, be ready to be looked for in terms of scenarios that are gonna say, where do you wanna place it? If you remember how the antennas are propagating signal, that's 90% of the issue. Also remember that you can take advantage of wifi analyzers to look for dead spots, and don't be afraid to move those WAPs around, nobody gets it right the first time.
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- Implementing wireless security
- Threats to your wireless network
- Wi-Fi Protected Setup
- Installing a wireless network
- Cloud ownership and implementation
- Creating a virtual machine
- PaaS, SaaS, and IaaS
- Mobile networking
- Deploying mobile devices