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DEMO: Networks

A hands-on exercise covering how to identify the network portion of IPv4 addresses using classful addressing rules, including Class A, B, C, and multicast address recognition.

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About this video

Classful IPv4 addressing divides the address space into distinct classes — A, B, C, D, and E — each defined by the value of the first octet. Identifying which class an address belongs to immediately reveals how many octets represent the network portion: one octet for Class A, two for Class B, and three for Class C. This classification is the starting point for understanding how IP networks are structured and segmented. Addresses in the Class D range (224–239) are reserved for multicast and do not follow the same network-host division that applies to unicast classes. Recognizing a multicast address and treating it separately is an important distinction that often appears in both academic assessments and real-world network analysis. Consistent practice with classful address identification builds the pattern recognition needed to work efficiently with IP addressing, subnetting, and routing concepts as they grow in complexity.

What you'll learn

What's covered

Identifying Network Portions of IP Addresses

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
2.2 Identify IPv4 addresses and subnet formats

Key terms

IP Address
A numerical label assigned to each device connected to a network that uses the Internet Protocol.
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.
Network Layer
Layer 3 of the OSI model, responsible for logical addressing and routing data packets between networks.
Classful Addressing
An early IPv4 addressing scheme that divided the address space into fixed classes (A, B, and C for hosts; D for multicast; E reserved) based on the leading bits of the address, with each class defining a fixed boundary between the network and host portions. Classful addressing was replaced by CIDR because it wasted large blocks of address space.
Network Portion
The bits of an IPv4 address that identify the specific network, determined by the address class in classful addressing.
Multicast
A transmission type in which data is sent from one source to a specific group of devices that have subscribed to a multicast group address, rather than to all devices or just one. This differs from broadcast (all devices) and unicast (one device).

Transcript

I did get a little note on here that says assume all classful addresses. It's really the only thing we know at this point, so I probably didn't need to include it, but I just wanted to specify that, because at some point in time that's going to change a little bit. We're going to go through this exercise a few times as we learn and grow and understand more.

So what we're going to do with this exercise is we're going to identify the network portion of this, the network bits. And so what we have to do is look at each one of these, take a look at the first octet, and figure out what range it is. I probably shouldn't circle that, because that's part of the exercise. Figure out what range that is. So it's 182, which falls in this class B right here, which means it's two octets that designate the network portion of this. So the network portion of this class B is the first two octets, and I'm going to circle that.

All right, I go on to the next one: 147, which falls into that same range, two octets, so I'm going to circle that.

225 — I see that's a multicast address, so I'll make a note here that it's a multicast address, which doesn't have the same network bit designator to it. So I'm just going to write down "multicast" there.

Make sure you have this information down, make sure you understand this. If not, practice it more. Continue to practice until you have this down, because you're really going to need to understand this concept of what octets are associated with the network side of these addresses.

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