Join Mike Meyers for an in-depth discussion in this video Introduction to Wi-Fi and wireless access points, part of CompTIA Network+ Exam Prep (N10-006) Part 6: Beyond the Typical Network.
- It seems that everybody uses WiFi today. I was just going through my house, and trying to count all the different devices that used WiFi. I've got my cellphones that use WiFi, I've got servers that use WiFi, I've got individual computers that use WiFi. I think somewhere around here I've probably got a blender that does WiFi. WiFi's been around for a long time, it's hyper popular, and it doesn't seem that anybody really understands it. So what we're gonna do in this episode, is cut it down to the very basics. So that's why I'm calling this "WiFi Basics." WiFi has been around for a long time.
Now when I say WiFi, we're talking about short-range radio to be used instead of cabling for distribution for local area networks. So the cornerstone to all this, is that in essence we're getting rid of wires, and replacing it with radio waves. So it's been around for a long time, but it wasn't until a company called "Linksys" began to sell little black and blue boxes, that the whole world started to really take off. The WiFi that we use is based on a standard called 802.11, or "eight oh two eleven." The 802.11 decides and declares a lot of very specific parts to a wireless network.
So let's go ahead and knock these out. So this is a wireless network card that I actually just pulled out of my desktop computer. And you can see it's got some antennas on it, and it acts as an interface to a wireless network. They don't all look like this. Here's a wireless NIC that's just a USB device, you plug it in and it handles all your wireless needs. In fact, wireless is so predominant today, that pretty much every mobile device from cellphones to pads, to netbooks to notebooks, they've all got wireless pretty much built in.
So wireless is ubiquitous, it's all over the place, and everybody's got a wireless NIC. Now a wireless NIC is great, but if you wanna plug into a network, you need a wireless access point, or a "WAP." This is an old WAP, I like this guy because it's kind of back when WAPs were made out of plastic, and how they really worked back then. Anyway, the important thing to appreciate is that a WAP is a bridging device that bridges between a wireless network and...
if you look in the back, there's an RJ45 connection, this plugs into a switch, a Ethernet network itself. So you have these two parts, you've got wireless clients and then you have a wireless access point. So with 802.11 you've got two choices on how you use this stuff. You have what's called "infrastructure mode" which is the most common, and then you have "ad hoc" mode. So to show you that, let's get out some blocks. In an infrastructure mode, we've got a wireless access point and then you have individual clients, and they're designed to connect to this wireless access point, and I'll show you how to do that in just a moment.
This is an infrastructure mode, you have a wireless access point. There's another option, it's actually kinda cool. Ad hoc mode, there is no wireless access point. All of these guys can talk to each other, but there is no inner connection to an Ethernet network. You can do some crazy things like bridge internet connection sharing or something like that to an individual system, but in ad hoc mode, there is no wireless access point, and in infrastructure mode, there absolutely must be a wireless access point.
When you set up a wireless access point, one of the most important things you're gonna be doing with this guy, did I just pick that up? (laughs) When you start configuring this guy, one of the most important things you're gonna be doing first, is you're gonna be setting up an SSID. An SSID is a name, and you'll actually get into these guys, most of them have web interfaces, and you go in you're going to set its SSID, which is a phrase that you can use, usually a small word, whatever you want to use, that declares that this particular wireless access point is broadcasting this one type of connection.
So when you take a wireless access point, and you set it up with an SSID, you've created the most basic form of wireless network there is, or a basic SSID, SSID stands for "service set identifier." So a BSSID is the more simple wireless network you can make with a WAP. It's going to be one WAP with one SSID that people are connecting to. What actually gets kind of cool, is that if you want to, you can take multiple wireless access points and connect them all to the same switch, and if you give them the same SSID, they will automatically start talking to each other and they will literally, if you're close to one wireless access point, he'll pick up your signal, and then as you go away from him and get closer to another one, that they're all connected to that same switch, that's the important thing, it will automatically pick up your connection and just keep going.
This is called an "extended SSID," or "ESSID." So, the basics is a "BSSID," but if you have multiple WAPS, all on the same SSID, you have an "ESSID." The SSID is simply the name of the network that's being offered up to the individual clients. Now those are the basics for 802.11, now there's a few other things that kick into play. For example, 802.11 is designed to run on two different, what we call the "ISM," or "industrial scientific "and medical bands." The ISM bands, there's a lot of these different bands, but the two bands that are used for 802.11, are the 2.4 gigahertz, and the 5 gigahertz band.
Now the trick is that the people who designed all this appreciated that there would be a lot of people out there setting up wireless networks. So, to make life a little bit easier, they came up with the concept of channels. Now the 2.4 gigahertz band one set of channels, the 5 gigahertz band has a much more complicated set of channels. And luckily for us, Network Plus is only interested in the 2.4 gigahertz band channels, you ready? The channels are one through 14, ta-da! That's about it. Well for North America, you can only use channels one through 11.
The rest of the world can use channels one through 13. In Japan, I don't know how they pulled this off, are the only people who can actually use channel 14. So your channels are, let's stick with the United States, one through 11. The problem with these channels is that they overlap fairly heavily. So here in the United States, the old rule is, there's really only three channels, one, six, or seven, and 11. And we usually only set our wireless access points to use one of those three channels, just to make sure that we're not overlapping, and to keep us away from other wireless access points that are broadcasting on the exact same channel.
Now I wanna take a minute and I wanna talk about something. Let's take a look at the back of this wireless access point. Now, when you look at the back of this wireless access point one of the things you're going to appreciate, is that this wireless access point has exactly one RJ45 coming out of it, and that's because all this guy is is a WAP, he doesn't do anything else. Let me show you something I bet a few of you are familiar with.
This is also a wireless access point, but I want you to look at the ports there. These ports, you can see there's more than one port on here, what's happening here folks, is that this is a home router. Not only is this a wireless access point, it's also a switch and it's also a router. This is three, three, three completely different devices all put together in one nice neat little box. There's nothing wrong with that, it's convenient and inexpensive, but you need to appreciate that when you're playing with a box like this, you have a router, you have a switch, and you have a wireless access point.
Just because they're all in one box, do me a favor, appreciate that it is three totally different devices, and each separate devices needs a separate kind of configuration. Most of these devices will have a webpage that you can do all your configuration, and there's no way to say "oh this is the WAP part," or "oh this is the switch part," or "this is the router part." It's simply telling you that all of these devices are combined. So next time you play with one of these home routers, remember it is a wireless access point, but it's also a router, and it's also a switch.
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