CompTIA Network+ N10-008 – Setting up a Virtual Network

1. GNS3 Walkthrough Example

Wide-area network technologies We’re going to break this lecture into two parts because there are just so many technologies that we have to talk about. The first is a dedicated lease line. Now this is a point-to-point connection between two sites, and you get all of the bandwidth all the time, which is great. This will include T1, E1, T3, and other dedicated circuits. Now, when you get this digital circuit, it’s going to be measured in 64Kbps channels called digital signal zero. and based on which connection you buy. For example, if you buy a T1, you’re going to get 24 of those 64-kilobit channels at your location. You’re going to get a device that’s like a modem, and it’s called a channel service unit, data service unit, or CSU DSU. This is what’s used to terminate the digital signal at your location and then tie it into your router to be able to connect it to your network.

So for exam day, I want you to remember that ones are dedicated lease lines, and they use CSU DSU to connect to your network. Now, what are some examples of digital signal levels? Depending on your carrier signal (T 1, T 3, E 1, and E 3) and digital signal level (DS 1, DS 3, for E ones and E three S), Those are the European standards, so they don’t fall into this digital signaling measurement. And then you’ll see the number of channels that you’re going to get and how many voice channels or 64 kilobyte channels you’re going to get. And your speed can be found on the right. What from this chart should you really memorize? You should be familiar with T1 and T3 speeds. And E1 speeds: if you remember that 1.54 megabits per second is a T 144.736, 45 megabits per second is a T 3, and 2.0 is an E1, you’ll be fine on test day.

Next. We have Metro Ethernet. Now, service providers are beginning to get away from those T1s, E1s, and T3 connections because those CSUs and DSUs have just been kind of cumbersome to work with. Instead, they’re starting to migrate toward metro Ethernet. This is where the service provider installs an Ethernet jack in your building, and you simply plug it into your router. They’re less expensive and more common than using specialised serial ports in a CSU DSU. And the technology used by the service provider really doesn’t matter to me as a customer. I don’t care what’s behind that Ethernet jack. I just want to be able to connect to my network. And so by giving me something as simple as an RJ-45 that I can plug into my router and get online, that’s a great win for the customer. And it enables the search provider to change the backbone at any time. And that’s the benefit of metro Ethernet. Next we have the point-to-point protocol, or PPP. This is a commonly used layer-two protocol that we use on top of these dedicated lease lines, whether we’re using Metro Ethernet, a T-1, an E-1, a T-3, or an E three.

And this is going to allow us to use multiple layer-3 protocols simultaneously, like IPX and IP. Most of the time, you’re probably only using IP in your networks. Each layer three control protocol runs an instance of PPP’s link control protocol, which manages that link and does some basic error checking for you. This will perform the multilink interface for you, allowing multiple physical connections to be bound together to form a single logical interface, similar to how link aggregation works in switches. You could do the same thing where I can buy two or three T batteries, bind them together, and get more speed. It also will do looped link detection to find any kind of errors for you.

It’ll also do error detection by checking your frames, and it will perform basic authentication over the link to make sure you’re authorized to use that point-to-point connection. And the way it does that is with three different mechanisms, depending on which one you choose. You could be using PAP, which is a password authentication protocol. You could be using the Challenge handshake authentication protocol, Chap, or Microsoft because they can’t seem to follow standards like everybody else, who made up their own called Ms. Chap, which is the Microsoft Challenge handshake authentication protocol. Now I say that a little tongue-in-cheek, but Microsoft actually made a better implementation of the old chat protocol when they made Microsoft Chat. Now, PAP, how does it work? Well, it performs one-way authentication between the client and the server. So in my basic diagram here, you’ll see I have a client on one side and the server’s router on the other. The credentials are sent in clear text from the client to the server. Basically, here’s my username and password, and the server comes back and says, “I acknowledge it, and I let you in.” Right, the bad thing about this is that PAP is in clear text, which means anyone can read your authentication and steal it from you. So we had to come up with a better way. And that’s where Chap comes in.

Chap is the Challenge Handshake authentication protocol, and it performs one-way authentication using a three-way handshake. So, when you want to connect to a router, in this case the server’s router, it begins by performing a challenge. Essentially, it says, “Hey, who are you?” Then the client will go back and say, “I am this person; here’s my username and password.” The router then checks the hashed credentials you sent of username and password, and if they match its stored version, it will send a success or failure message. Now, Microsoft’s version does the same type of thing, except there’s a two-way authentication there where the client verifies the server and the server verifies the client. For the exam, I want you to remember that PAP is in the clear, and that is a huge security risk. Chap and Microsoft Chap actually hash the credentials, making it a more secure way of doing PAP. Next, we have point-to-point protocol over Ethernet, or PPPoE. This was commonly used with DSL modems, and it actually took your PPP protocol that we would use over AT1, and it would encapsulate those frames within Ethernet. If you’re using Metro Ethernet, you’re likely using this as well. This allows for authentication to occur over Ethernet using something like PAP Chap or Microsoft Chap. Next, we have DSL, or digital subscriber line.

Now, when I first started building networks back in the late 1990s and early 2000s, DSL was all the rage. It was everywhere because it was a very inexpensive way to get high-speed data to our end users and our small office and home office environments. Instead of having to pay for a T1 connection, which may have cost us several hundred dollars a month, we could buy a DSL connection for $50 or maybe $100 a month. Now, there were three different types of DSL. ADSL, SDSL and VDSL. Now, ADSL is asymmetric DSL, and what that means is there’s a different speed on the download versus the upload. The maximum download speed was about eight megabits per second, according to current textbooks, although some were going a little bit faster than that. The upload speed was equivalent to a T1 with 1.54 megabits per second. Now, why would it be OK to have different upload and download speeds? Well, this goes back to the 80/20 rule. When you’re online, do you upload more or download more? For most of us, we download more. For example, when you’re watching this video right now, you selected the video with your mouse and told the server what you wanted to watch. That may have been one or two KB in size.

The video I sent you back is 100 megabytes or more in size, and so it’s a very, very large file, and you’re downloading all of that, but your upload was very, very minuscule. And for the majority of users, they upload very little, but they download a lot. So DSL maximised the downloads and minimised your uploads. SDSL, or symmetric DSL, worked just like T One. They would have equal upload and download speeds. Now, the speeds are much slower here for Symmetric, but they’re dedicated access, so you’re pretty much guaranteed that speed. With ADSL, if there were a lot of people on the line, it could actually slow down your speeds. Because ADSL was so popular with home users, it started getting a lot more funding, and the ADSL speeds increased quickly and got to those one and a half megabits per second, four megabits per second, and eight megs per second. When they first came out, they were all very slow, at about 256K or 512K. As technology progressed, they shifted more towards ADSL and abandoned SDSL. Now, the last one we have is very high-bitrate DSL. This is where you could get very, very high speeds. In fact, download speeds can reach 52 megabits per second and upload speeds can reach 12 megabits per second. Now, the big limitation here was your distance from the DSLAM. Now. What’s a DSLAM? That is the point of presence that is actually owned by the telephone company. So you could only be 4000 feet from them, which is less than a mile. So not all home users or offices could get VDSL, but most of them were within 18,000 feet and could get ADSL again. DSL has been declining in popularity in recent years as people have started moving towards cable and fiber, which we’re going to talk about.