TechKnowSurge
Cisco CCNA 1.13 CompTIA Network+ 2.2 Cisco CCST Networking 4.5 CompTIA Network+ 1.1
TechKnowSurge Catalog Videos MAC Address Types
VideoNetworkFree

MAC Address Types

Network communication relies on four MAC address types — unicast, broadcast, multicast, and anycast — each determining how frames are delivered across a network. Understanding how switches handle each address type is fundamental to layer 2 networking.

⚑ Complete this video to capture a CTF flag worth 1 point.

About this video

At layer 2, network communication is governed by four MAC address types: unicast, broadcast, multicast, and anycast. Each type defines a different delivery model, and switches handle each one differently based on the destination MAC address embedded in the frame. Unicast is the most common model — a frame carries both a source and destination MAC address, and the switch forwards it only to the port associated with that destination device. Broadcast uses the reserved address FF:FF:FF:FF:FF:FF, a string of all ones, which signals the switch to flood the frame out every active port. A typical use case is the Address Resolution Protocol, where a device knows a target's IP address but must discover its MAC address before it can communicate across the local network. Every device receiving the broadcast can inspect it, and the intended recipient replies with its MAC address. The entire layer 2 segment where this flooding occurs is known as a broadcast domain. Multicast operates as a one-to-many model, targeting a defined group of devices rather than all of them. When a switch receives a frame with a multicast destination address, it forwards it only to the ports associated with devices that are part of that multicast group. This can be configured statically by an administrator or managed dynamically, where devices subscribe to a multicast address and the switch learns which ports should receive that traffic accordingly.

What you'll learn

What's covered

MAC Address Types

Aligned to

Cisco CCNA
1.13 Describe switching concepts
CompTIA Network+
2.2 Given a scenario, configure switching technologies and features.
1.1 Explain concepts related to the Open Systems Interconnection (OSI) reference model.
Cisco CCST Networking
4.5 Explain basic switching concepts

Key terms

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.
Switch
A network device that connects devices within a LAN and forwards traffic based on MAC addresses.
Data Link Layer
Layer 2 of the OSI model responsible for node-to-node data transfer and error detection on a single network segment.
Address Resolution Protocol
ARP
A protocol used to map an IP address to a physical MAC address on a local network.
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).
Broadcast Domain
A network segment in which a broadcast sent by one device is received by all other devices within that segment; routers define the boundaries of broadcast domains by not forwarding broadcast traffic.

Transcript

When it comes to communicating on our networks, we have unicast, multicast, broadcast, and anycast. We've largely talked about unicast, and a lot around MAC addresses and what unicast MAC addresses look like. But what do the rest of them look like?

Unicast

Unicast happens just as what we mentioned before. There is a destination MAC address that gets added to the frame as it's sent out the network interface card, and it has a source MAC address as it's sent out. It gets from one location to the next because the switch recognizes what destination MAC address it's going to, and then forwards it out the port to get it to that device that owns that MAC address.

Broadcast

A broadcast is a message that's going to be sent, and the switch will actually broadcast that out all live ports. An example of a broadcast may be an ARP request. We know that if we have an IP address of a server but need the MAC address of the server so we can send it information across this LAN, we need to do address resolution. So we use the address resolution protocol. We send it out, and that request goes out all ports. This machine gets it and sends back the response with a MAC address, so that this machine can turn that IP address into a MAC address and send it out.

But the problem is it doesn't know the destination where that's going to go to. So what it does is it sends out the ARP request with a destination address of FF FF FF FF FF FF. That series of all ones, essentially, if you look underneath it there, that series of FFs that gets sent out, lets the switch know this is going to be a broadcast, and then that switch will broadcast it out.

So this is a broadcast, and everything that happens within this local area network, anything that is sent to this address right here, we call that a broadcast domain. So everything within this layer 2 here is a broadcast domain.

Multicast

A multicast frame is used to send data to specific clients, so it's a one-to-many. Let's say this machine wants to send to a couple of different clients on the network at the same time. It could use a multicast frame to do that. So as it sends it out to the switch, the switch recognizes that it's a multicast, and will send it out those ports only, to those machines.

Of course, this switch does need to know which ports to send based on that multicast address, and so it will do that in several different ways. You can either program the switch to do multicast on certain ports, so that switch knows what ports to send it out, or there are some dynamic ways for this switch to learn and make sure that these devices check in or subscribe to that multicast address.

About TechKnowSurge

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 →