Unicast, Multicast, Broadcast, and Anycast: The Four Modes

How a packet is addressed determines how it is delivered by switches and routers. Here are the four fundamental patterns.

1. Unicast (1-to-1)

The standard. One source sends to one destination. Most web browsing and email is unicast.

2. Broadcast (1-to-All)

One source sends to every device on a local network. DHCP use broadcast to find servers when joining a Wi-Fi.

3. Multicast (1-to-Many)

One source sends to a specific group of interested devices. Used for IPTV and video conferencing within corporate networks.

4. Anycast (1-to-Nearest)

One source sends to the "closest" of many destinations sharing the same IP. This is the foundation of high-speed DNS and CDNs.