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What’s an IP Address?

IP addressing is a hierarchical system that enables data to be routed accurately across global networks by organizing addresses into manageable, delegated ranges. Unlike MAC addresses, which are fixed and only practical on local networks, IP addresses can be dynamically assigned and logically structured to support worldwide communication.

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About this video

Sending data reliably across a global network requires more than just identifying a destination — it requires an addressing system with enough structure to make routing decisions at every step along the way. MAC addresses, which are permanently assigned by hardware manufacturers, work well for identifying devices on a local network, but they offer no logical hierarchy. Routing traffic globally based on MAC addresses would demand a single, planet-scale database mapping every address to a physical location, which is neither feasible nor secure. IP addressing was designed specifically to overcome this limitation. IP version 4 addresses are 32 bits long and written in dotted-decimal notation, divided into four octets — for example, 192.168.40.41. The hierarchical structure of this system allows large blocks of addresses to be assigned to broad geographic or organizational regions, which then subdivide those ranges further until traffic is narrowed down to a specific network and device. This delegation model is administered globally by IANA, which distributes address blocks to regional authorities, who in turn allocate them to internet service providers and organizations. Because IP addresses are logically assigned rather than burned into hardware, they can be dynamically configured each time a device connects to a network. A laptop connecting to a different network will receive a new IP address appropriate to that network's range, ensuring that any packet destined for that device can still be routed correctly from anywhere in the world. This combination of hierarchical structure and dynamic assignment is what makes reliable global communication possible at scale.

What you'll learn

What's covered

IP Addressing

Aligned to

CompTIA Network+
1.7 Given a scenario, use appropriate IPv4 network addressing.
Cisco CCNA
1.6 Configure and verify IPv4 addressing and subnetting
Cisco CCST Networking
2.1 Compare and contrast private addresses and public addresses
4.4 Explain basic routing concepts
2.2 Identify IPv4 addresses and subnet formats
CompTIA A+ Core 1
2.6 Compare and contrast common network configuration concepts.

Key terms

IP Address
A numerical label assigned to each device connected to a network that uses the Internet Protocol.
Internet Protocol
IP
The principal communications protocol for routing packets across network boundaries.
Packet
A unit of data formatted for transmission over a network, containing a header, payload, and sometimes a trailer.
Media Access Control
MAC
A sublayer of the Data Link layer that controls how devices on a network gain access to a medium and transmit data.
Router
A network device that forwards data packets between networks based on IP addresses.
Octet
One of the four 8-bit sections of an IPv4 address, each separated by a dot in dotted decimal notation and representing a decimal value from 0 to 255. For example, in 192.168.1.1, the four octets are 192, 168, 1, and 1.

Transcript

It is wild how we can send messages across this planet in milliseconds with a touch of a button - how I can type something out and hit enter and it just gets to where it needs to go. But there's addressing involved with that. Specifically, there's IP addressing. That IP addressing lets that information know how to get to where it's destined to.

Why MAC Addresses Are Not Enough

When we're communicating on a local area network, what we're going to be using is these MAC addresses. So to address devices on the network, we're going to send it to a MAC address. Now, what's interesting about these MAC addresses is they're burned in on the machine. So whoever manufactured this machine, or specifically the NIC on the machine, assigned it some sort of MAC address. And the next sequence in this MAC address, which would end in the 85, probably got sent to another location, someplace far away maybe.

And so these burned-in addresses have a big weakness. How would you find a specific MAC address in the world? We would have to have a huge database on all the locations of all the computers. Not to mention, there's a security risk with that. But we would have to just have a crazy database that's simply not manageable if we were to use these MAC addresses as a form of routing information, of sending information across this planet. It's just not feasible. MAC addresses only really work on a local scale, a local level.

Hierarchical Addressing

Instead, we need some sort of hierarchy addressing. That's what IP addresses give us. We could represent all of IPv4 addresses using this address right here, and then we could split it down into smaller components. So you can see an 8, a 9, a 10, 11, 12, 13. We could take a block of those and we can assign it to some sort of country or some sort of area. And then from there, all we need to do is if there's something within this range, we just send it to that area, and then they figure out what to do with it from there. Then it's out of our hands and they have to figure it out.

And then in that area they further break this down. Let's take this 10 network right here - it can be broken down into, we see 97, 98, 99, 100, 101. So this address gets broken down into all of here. So whatever gets sent could be sent to here, which then could be sent to here. And then this could be further broken down into smaller networks. We can see 97, 98, 99. This is all for the third octet now. So we see that this is all broken down, and it could be sent then to wherever it's going to be next, and so on and so forth.

So the point here is that IP addresses are a hierarchy address, and hierarchy addresses allow us to have kind of these scopes that we divvy out to certain entities. Whether it be - there are some entities out there that we give it to, and they would give it to internet service providers, and they give it to businesses, and then the businesses would divvy it out amongst their network. And we'd still be able to route traffic all across this planet because it's a hierarchy addressing scheme.

What an IP Address Looks Like

So what does an IP address look like? Well, it's 32 bits long. So this is what it looks like to the computer, in computer language. But when we want to read it, it gets broken down into a little different visual for us so that we can read it. It's in decimal format, so we see more familiar numbers: 192.168.40.41. And then it's broken up into these octets, so we break it up with these dots here. So we read this 192.168.40.41.

Now, as we see with the MAC addresses, they're really quite random as to which ones we have on our network, because we probably bought these machines maybe from different vendors, probably from different times, and so we get different ranges of these MAC addresses. However, what happens is when a machine connects to this network, then it gets an IP address. And so usually we have dynamic configuration for these, and so it will get an IP address when it connects to the network. If you were to take that laptop and move it and connect it into a different network, then it would get assigned a different IP address in a different range. And that once again is so that way any packet in the whole world, any message in the whole world destined for this device, can get there with this assignable IP address.

Who Hands Out the Addresses

Of course, if we have some sort of hierarchy addressing, we also have entities that are responsible for certain sections of that. So we've got IANA, that's responsible for the big overall, that divvies out amongst these different areas, and these are who is in control of those different areas. So we divvy out who's responsible for these different areas and assigning IP addresses, and then these entities are responsible for divvying out whatever ranges they were given into smaller ranges within their area.

So when it comes to an IP address, in this example it's 48.51.46.55. Maybe I'm sending a message to this. It can get sent to the right place. And I don't know which area this one actually goes to, but it'll send it to the right area, which will then send it into the right area as part of that area, and narrow it down to wherever it needs to go.

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