This content covers how IP addressing, subnetting, and VLSM are applied to a real corporate network environment, including how to assign network addresses, broadcast addresses, and usable host ranges across 31 distinct networks. It also introduces the distinction between Layer 2 and Layer 3 networking as foundational context for practical address planning.
Applying IP Addressing Concepts
It's one thing to learn the concepts and understand how to do IP addressing and subnetting and VLSM. It's a whole other thing to know what it actually means when you get into the outside world, the real world, and are actually applying it. So this is a setup for how we take this information and apply it to what we'd see out there.
Here's the network of a company that we are the network engineer for, and one of our jobs is going to be to assign IP addresses and ranges to these different networks on here. We're going to build off of this in future modules.
One thing to understand here is that all of this is a corporate network that we're going to be managing. We have this network that we're going to have to manage, but within this network there are a lot of networks. What I mean by that is you could consider each one of these branches right here a network, a network of machines that's delivering services to a lot of endpoints. You see the number of endpoints here: this has 134, this has 45, this has 98, this has 758. Each one of these has a bunch of endpoints on it, and we're delivering connectivity to these different devices out there. That's what a network does -- it delivers connectivity to all of these end devices.
But there's also another type of network here. Between all of these, we have interconnections, and I can circle all of them here. You can see that there's quite a few. When you add these all up, we have a total of 31 networks here. So we have 31 networks within this big corporate network.
Just understanding the difference with that: for each one of these, we've talked about having a network address, so each one of these will have a network address, each one of these will have a broadcast address, and then a usable host range. Some of them are not going to need that many, such as we've got 45 here or 14, and others are going to need a lot of usable hosts, like this one has a 1 351.
There are actually these links right here where possibly we just need two, one for each side of this connection here. So there are going to be times when we just need two usable IP addresses, and times when we need a large quantity of these IP addresses.
I had mentioned this earlier, but I'm just going to call it out again: the difference between a layer 2 and a layer 3 network. We haven't gone over the OSI model and what the difference is between layer 2 and layer 3, but a lot of it is just how things communicate.
From a layer 2 perspective, it's considered your local area network -- or at least from an Ethernet standpoint it's considered your local area network -- and that is just devices that are on the same network that are communicating. There's a set of equipment that helps that communication happen, generally switches, but there are other communication devices that happen in layer 2 as well.
Versus layer 3, which is these connections, these devices right here. These are layer 3 devices. These happen to be routers right here. There are other devices that are layer 3 devices, but in our example here we just have routers that are interconnecting all of these different devices. So this is layer 3.
Within this, when we're talking about networking, when we're doing IP addresses and when we're doing subnetting and when we're doing all of this, we're really talking about that layer 2 network here -- which I circled in my last slide, but it'd be all of these where the end users are -- and then these links between these layer 3 networks.
Once again, the communication could be a little different. Ethernet could be on these LANs here, versus there could be some other type of connection that goes between these devices. So there are a lot of options, and it gives a lot of flexibility. Really that's a big part of the OSI model: to break things down into different layers to give flexibility and to be able to develop things at a layer level without affecting the other layers.
This course doesn't really get too much into the OSI model, but I just wanted to introduce those terms and give you some context as we move forward. We're going to be using this for applying what we learn, through our different steps and through our different modules, to what you'd actually see when you get out there.
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