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Unicast, Multicast, Anycast, and Broadcasts

Unicast, multicast, anycast, and broadcast are four distinct methods for directing network traffic, each differing in how many devices receive a given transmission. Understanding these addressing types is foundational to network communication and traffic management.

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About this video

Network communication relies on different addressing strategies to control how traffic flows from a sender to one or more recipients. Unicast is the most straightforward model, establishing a direct path between a single sender and a single destination device. At the opposite end of the spectrum, broadcast transmits a message simultaneously to every device on the network, regardless of whether those devices need the information. Multicast occupies the space between these two extremes by delivering traffic only to devices that have opted in by subscribing to a shared multicast address. This one-to-many model improves efficiency over broadcast by limiting delivery to relevant recipients without requiring individual unicast sessions for each one. Anycast refines this concept further by associating multiple devices with a single address but routing any given request to just one of those devices rather than all of them. Anycast is particularly valuable for service redundancy. When multiple servers provide the same service and share an anycast address, the network directs each incoming request to the most appropriate single instance, distributing load and maintaining availability without exposing the client to that complexity. This behavior makes anycast a hybrid of multicast and unicast principles and a critical tool in resilient network and service design.

What you'll learn

What's covered

Network Communication Types

Aligned to

CompTIA Network+
1.4 Explain common networking ports, protocols, services, and traffic types.
Cisco CCNA
1.9 Describe IPv6 address types
CompTIA A+ Core 1
2.6 Compare and contrast common network configuration concepts.
Cisco CCST Networking
1.1 Identify the fundamental conceptual building blocks of networks

Key terms

Unicast
A transmission type in which a packet is sent from one source directly to one specific destination device, identified by its unique IP or MAC address. Unicast is the standard delivery method for most internet traffic such as web browsing and file downloads.
Broadcast
A transmission type in which one device sends a single packet that is delivered to every other device on the local network segment simultaneously. Broadcast traffic is contained within a broadcast domain and does not cross router boundaries.
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).
Anycast
A transmission type where data is sent to an anycast address and delivered to only one of several devices associated with that address, typically the nearest or best-available one.
Redundancy
The duplication of critical components or systems to increase reliability and availability.

Transcript

Let's take a look at the difference between a unicast, a multicast, an anycast, and a broadcast.

First up, unicast. Unicast is just one device that's sending to another device. So it's directed traffic, that is only going to one destination.

Broadcast, on the other side, is when a device sends out a message that makes it to all devices. So this is a broadcast.

Now multicast is a little different. It's in between a unicast and a broadcast. There are certain devices on a network that subscribe to a multicast address. Then when a device wants to speak to those devices, it will send it to that multicast address, and it gets sent out to these devices. So it's a one to many, but it's not a one to all.

Anycast is something in between a multicast and a unicast. What it is, is that we want redundancy within our services. Maybe we have multiple machines that are providing some sort of service, and what will happen is that we need to request a service from one of those machines. So we send a request to an anycast address. Devices on the network know which devices those are associated with, and will send it to one of the devices, but not all of the devices. So it's similar to a multicast, in that there's multiple devices that are subscribed to this address, but it's similar to a unicast in the sense that the message is only going to get sent to one of the machines.

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