Seonglae ChoDefinition
Anycast is a method that sends traffic to the nameserver closest to the client through network routing.
Method
Data transmission to only one node among the receivable closest nodes connected to the network
Results
When using Anycast, the burden of nameserver selection shifts from the Resolver to the routing system (BGP), which can provide better performance.
The optimal approach for a domain when considering both performance and operational resilience is for the domain to be served by two distinct dual-stack diverse anycast nameservers.
While it may seem that increasing the number of nameservers would improve stability, in reality there are no significant benefits to having more than 6 servers.
For domains with DNSSEC enabled, nameserver configuration and key management become more complex. This requires additional considerations.
ISP Column - December 2024
It's common folklore in the Domain Name System that a delegated domain name must be served by 2 or more nameservers. The logic for this is based in a desire for service resilience. If one server is unreachable then hopefully the other is not, and recursive resolvers when presented with a list two or more nameservers for a domain will work through this list until it queries a nameserver that is responsive.
https://www.potaroo.net/ispcol/2024-12/nameservers.html
blog.cloudflare.com
https://blog.cloudflare.com/cloudflare-servers-dont-own-ips-anymore/