Subtitles of the Movie

Let's continue our discussion of IP addressing with a closer look at the IP address itself and all the parameters of an IP address. These are things that again you may have heard of before in classes maybe like an A+ class or Network Plus type of a class or tutorial, but there's certainly things that we need to make sure we understand as we set the table and use Server 2003 to manage IP addresses. One thing to understand about IP addresses is that all IP addresses are a 32 bit number. When I look at an IP address that's been assigned to my computer and one of the ways I can quickly display my IP address, is by opening up a command prompt, start, run, cmd and then typing the command ipconfig, This shows me the IP configuration parameters that have been assigned to my computer, and we'll talk about this utility in more detail later on. This address here is really 32 ones and zeros, that is the meaning of 32 bits. We deal with them one octet at a time, in other words 8 ones and zeros at a time and we convert that octet to decimal and we spend the next module, talking about binary addressing and dealing with the octets the way that computer see the octets. But just something to know right of the bat is that 100 is not a number that the computer deals with, at least not in decimal notation, it deals with 100 as a series of ones and zeros, same thing with 168, same thing with 192. Each and every IP address in every part of the 32 ones and zeros, there are some of the ones and zeros that represent the network portion, and some of the ones and zeros represents the host portion or the host identifier. To show you what I mean I've prepared a little, just a basic network here. This is about the most simple network you can imagine here on the Paint program. Here we have a network and we can call this network network 1 and we can call this network network 2. Two networks separated by a router. What's a router? It can be, just the basic definition is a computer with two network cards. Now most routers that we deal with are dedicated machines to do just that, but you can easily configure any computer to be a router with, just install two network cards. So the router actually exists on both network 1 and network 2. So if we had an IP scheme that only had to deal with two networks, we might give this computer IP address of 2.1 in other words the one computer on the two network and this computer 2.2, something like that and maybe the router interface 2.3 So this is all network 2. Network 1, 1.1 1.2 1.3 and so on and this would be the 1 network. But IP, as it is scalable allows for many networks, hundreds of networks, thousands of networks, millions of networks. So we have a numbering scheme that is just a bit more complex. So for example the IP address that's been assigned to my computer is 192.168.2.100. How do we tell a part in an IP address what's the network identifier and what's the host identifier. We do that with the subnet mask. Subnet mask here in this case is 255.255.255.0 and this shows me the dividing line. So the mask's job is to separate the network portion from the host portion. This portion is the network identifier, so my computer lives on the 192.168.2 network and it's host number 100 on that network. Now notice that with a subnet mask of 255.255.255 it's very easy to see that dividing line but to the computer, this is just a string of ones and zeros mixed and matched but this is all ones followed by all zeros and that's something to keep in mind as we progress to the next module. It's easy to see in this instance, it's not in all instances. Some of the rules about configuring IP addresses, let's go back to the slide show here, the rules are these. All network IDs must be unique and all hosts must be unique for a given network. Show you what I mean, let's go back to our simple hypothetical network, if we were to add another network to this, if this was our Internet, we could not build this network and call it the 2 network. We couldn't call it the 1 network, we would have to call this network the 3 network and then this would have to be 3.1 and then within this network we couldn't reuse the host identifier of one. We'd have to call this one 3.2. The rule is that the host identifier must be unique to the network. So is one unique throughout the entire Internet, no but it's certainly unique within each network. So those are the two rules or two of the rules that we want to discuss for right now. When you configure an IP address you will commonly configure the big three, what I call the big three, the IP address and the subnet mask have been discussed earlier. There's the IP address, the number that's assigned to your computer, the subnet mask helps separate that number into a network identifier and a host identifier. What's also commonly configured is the default gateway. The default gateway is not required by IP addressing, so you don't have to have it but if you want to communicate with other networks you need a default gateway. The default gateway is your computer's pathway to other networks. If we're sending a packet of information that belongs to any other network, besides the 192.168.2 network, we're going to deliver that packet to the network interface 192.168.2.1. In our example here, what's the default gateway of this computer here? 1.3 What's the default gateway of 2.1? 2.3 In order for a packet to get from here to here or from here to here, it goes through this router interface. That's the third very important parameter of IP addresses. The IP address, the subnet mask and default gateway. It's very important that you understand the job of each of these three things as we go forward and look at IP addressing.