Unicast, multicast, and broadcast addresses

There are three types of Ethernet addresses, Unicast address, multicast address and broadcast address.

1. Unicast addresses

Unicast addresses represent a single LAN interface. Also, a unicast frame will be sent to a specific device (represented by green line in the below figure), not to a group of devices on the LAN:

Unicast, multicast, and broadcast addresses

The unicast address will also have the value of the MAC address of the destination device.

2. Multicast addresses

Multicast addresses represent a group of devices in a LAN. Also, a frame sent to a multicast address will be forwarded to a group of devices (represented by green lines in the below figure) on the LAN:

multicast

Multicast frames have a value of 1 in the least-significant bit of the first octet of the destination address. This then helps a network switch to distinguish between unicast and multicast addresses. One example of an Ethernet multicast address would be 01:00:0C:CC:CC:CC, which is the address that CDP (Cisco Discovery Protocol) uses.

3. Broadcast addresses

Broadcast addresses represent all devices on the LAN. Also, frames sent to a broadcast address will be delivered to all devices (represented by green lines in the below figure) on the LAN:

The broadcast address has the value of FFFF.FFFF.FFFF (all binary ones). Also, the switch will flood broadcast frames out of all ports except the port that was on the receiving end.

If you have any queries about the three types of ethernet addresses namely Unicast address, multicast address and broadcast address, feel free to post your questions in the comments.

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