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.
Figure - IP Anycast vs. Unicast
CDN service providers who configure their platform with Anycast set a single IP address for all their nodes!
Orhan Ergun, CCIE/CCDE Trainer, Author of Many Networking Books, Network Design Advisor, and Cisco Champion 2019/2020/2021
He created OrhanErgun.Net 10 years ago and has been serving the IT industry with his renowned and awarded training.
Wrote many books, mostly on Network Design, joined many IETF RFCs, gave Public talks at many Forums, and mentored thousands of his students.
Today, with his carefully selected instructors, OrhanErgun.Net is providing IT courses to tens of thousands of IT engineers.