A local area network (LAN) connects devices within a defined physical boundary, with a router marking the edge where local traffic—broadcasts, collisions, and related security concerns—stops before reaching the wider network. The IEEE 802 standards formally define the protocols governing how LANs communicate, though the conceptual and protocol-based definitions of a LAN don't always perfectly align.
Local Area Network (LAN)
One thing that we need to be really familiar with is the LAN, or local area network. It's something that's going to come up often.
When it comes to local area networks, I feel like there are two definitions here, and they're pretty close to the same thing except for little nuances, little differences. One is that there are protocols out there that define what a LAN is and how it communicates; there are specific LAN protocols. Then there's the concept of what a LAN is. Many times when we talk about LANs, we're talking about the concept. I want to clarify that because there are times when we talk about the opposite of what a WAN is, and we still may use the same LAN protocols for those WANs, so it gets a little murky at times. So we're going to mainly talk about the concepts, and then I'll introduce you to what I mean by the protocol.
Really, a LAN is just what we've been talking about this whole time. It's local because all of these devices have local connectivity to each other. One thing that's interesting about a local area network is that they can be prone to collisions, not always, but they can be. For instance, this is a hub, and so we have collisions that happen within here; we call this a collision domain. We can do away pretty much with collisions by replacing this hub with a switch. So just because it's a local area network doesn't mean that we have collisions, but initially when this was created, this was a network that did have collisions.
Another thing we see in a local area network with all these devices connected together is that there are some security concerns. With a hub, information gets sent out to all devices. Any communication going between one device and another gets seen by all other devices. So there are some security concerns, although we do away with much of that by using a switch instead of a hub.
Another thing we see within our local area network is broadcasts. That's that FF FF address. When things get sent out to that, it gets sent out to all devices on the network. Everything is listening, and rightfully so; that's what a broadcast is intended to do. So even if we replace this hub with a switch, we would still have broadcasts on this network.
Now imagine that on a global scale. If we had collisions on a global scale, if everything was being broadcast out to all devices, just the amount of broadcasts from all of these devices all over the internet would be so much traffic, from broadcasts alone, that no one would ever get any work done. Which is why we need to compartmentalize, or split off, or segment certain parts of our network. What we do is add a router, and the router is the edge point of our local area network. Here we have the boundaries of our local area network, and within here we can have collisions, we have some security concerns, and we have some broadcasts that happen when we're sending to that specific MAC address we mentioned. But that all stops at the router. Although we could still have some security concerns at the router and there are things we need to address from that perspective, essentially our local area network ends right here at the router.
Let's take a different perspective. Let's look at how many LANs are within this diagram. We have routers here, and the routers are going to be routing information on a more global scale. Then we have this network that's interconnected by this switch or hub, and this is a LAN; we'll call this LAN A. Then we have another one over here, and this is another LAN; we'll call this LAN B. Everything in between here we're not going to get too much into right now, but this is a WAN. So that's the concept level of what a LAN is.
Now let's look at the protocol. Here we see the IEEE 802, and this is a standard that's out there. I don't want to get too in depth into what this is, but essentially the 802 is a bunch of different protocols that all fall under this 802 heading, and this is the standard that defines these local area networks, what these LANs are. So we have specific protocols that are tied to what a LAN is. The reason I mention this is because, from a concept level, this is a LAN and this is a LAN, and this is a WAN, but we could possibly use those 802 links in between here. The technology that's specified by the 802 we could use in between here, so they're kind of like LANs, but we call them WAN connections. That's where the concept and the protocol split a little bit. For the most part, when we're talking about the concepts, understand that these are the LANs, and then this would be our wide area network, which we'll further define in another video.
TechKnowSurge builds IT and cybersecurity professionals through hands-on, concept-first training built around real understanding — not memorization. Free interactive tools, structured programs, and 25+ years of real-world experience, all in one place.
Explore free tools and programs →