What is IP Anycast? Is IP Anycast a routing protocol? Where IP Anycast is used in Networking?. In this post, I will answer these questions. I discuss these questions and often ask them in my training as well. I always receive many different answers but you will see how it is easy to understand the idea behind anycast after reading this post.
IP Anycast is a way of assigning IP addresses. The same IP address is assigned to multiple nodes. It is not a routing protocol, switching protocol, or a special network design. Just a way of assigning an IP address. There are many use cases for it. Internally in the networks, Multicast uses IP Anycast for load balancing and redundancy.
Specifically, PIM ASM (Protocol Independent Multicast - Any Source Multicast) uses IP Anycast for the RP (Rendezvous Point) address assignment. The same IP address is assigned on multiple nodes in the network and the underlying IGP protocol shortest path is used to determine the closest RP in a topology.
IP Anycast for CDN (Content Delivery Networks)
IP Anycast is a special method for request routing in CDN architecture. Let's have a look at what is request routing and how Anycast is used in request routing. Request routing or also known as server redirection is a method to bring the customer to the optimal server in a CDN architecture.
Figure - IP Anycast vs. Unicast
CDN service providers who configure their platform with Anycast set a single IP address for all their nodes!