Anycast Routing: How to Be Everywhere at Once

In traditional Unicast, one IP address belongs to one machine. In Anycast, the same IP address is announced by many different routers in different parts of the world.

The Nearest Node

When you send a packet to an Anycast IP (like 1.1.1.1), the internet's core routers use BGP to find the "shortest" path. Usually, this means you end up at the server physically closest to you.

Self-Healing Networks

If the Anycast node in London goes down, BGP will automatically start routing UK users to the next closest node, such as Paris or Amsterdam. This happens without any changes to DNS records, providing incredible uptime.

Anycast is the "secret sauce" behind every major CDN and high-speed DNS service today.