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TechKnowSurge Catalog Videos DEMO: Broadcast Addresses
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DEMO: Broadcast Addresses

A broadcast address is the final address in a network range, used to reach all devices on that network simultaneously. This concept also explains why two addresses are always subtracted when calculating the number of usable hosts on a subnet.

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About this video

A broadcast address is the last IP address in a network's range and serves as the destination for traffic that must reach every device on that network simultaneously. This stands in contrast to unicast communication, which targets a single host, and multicast communication, which targets a defined group. Understanding where the broadcast address falls within a range is a foundational skill in IP addressing and subnetting. Identifying the broadcast address depends on knowing the class of the network, which determines how many octets belong to the network portion of the address. For a Class C network, the first three octets are fixed as the network identifier, and the broadcast address is formed by setting all bits in the final host octet to one, yielding a value of 255. For a Class B network, the first two octets are fixed, and both remaining octets are set to all ones, producing a host portion of 255.255. This concept also clarifies a standard rule in host calculation: when determining the number of usable addresses on a subnet, two addresses are always subtracted from the total range. One is the network address at the start of the range, and the other is the broadcast address at the end. Neither can be assigned to a host, so they are excluded from any count of available addresses on that subnet.

What you'll learn

What's covered

Broadcast Address

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.
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.
Subnet Mask
A 32-bit number that divides an IP address into network and host portions.
Broadcast Address
The last address in an IP subnet range, formed when all host bits are set to one, used to send a single packet to every device on that network simultaneously.
Network Address
The first address in an IP network range that identifies the network itself and cannot be assigned to a host. It is formed when all host bits are set to zero.
Subnet
A logical subdivision of an IP network, used to organize and segment network traffic.

Transcript

So what is a broadcast address? We've already identified what a broadcast is. You have unicast, which is one machine to another. You have a multicast, which is one machine to multiple other machines. And you have a broadcast, which is from one machine to all other machines. So a broadcast address is just an address that you can send information to and it will reach all machines on that network.

Finding the broadcast address

The broadcast address is the last address of the range. If we take a look at one of these networks right here, we can identify this is a Class C, that makes the first three octets the network portion of this address. The first address of the range, which in this case is .0, would be the network address. So this is the network address for this.

The broadcast address is the last address of the range. So that would be .11111111, or we could say 255. So the broadcast address for this range is 192.168.1.255, and that is the address that's going to reach all devices on this network.

I could do the same thing over here. It's a Class C. The first three octets are the network side of it. This is the network address. And the last in this range is 192.168.0.255. So that is the broadcast address for this network over here.

Why we subtract two

I'm going to just do a little bit of a callback to where we talked about the nodes — or you could also replace that with hosts — of this network. That is how many usable addresses there are. So if I were to say that this is how many usable addresses there are, then I have to subtract two, and the reason why I have to subtract two is because I have the network address and the broadcast address. So that's why we subtracted two from the usable range there.

A Class B example

Here again, you can do this practice. I'm going to take a look at this. This is a Class B, which means that the first two is the network portion of this. So I know that the broadcast address is going to start with 144.22, and then it's the last of this range. So the last of this range, all the host portions of this, would be all ones. So it would be 255.255. And that's how I find the broadcast addresses of this range.

Continue to practice this and go over this until you know that you have it down, because we are going to be using this quite a bit through the rest of this course.

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