How does anycast routing work and what are its use cases?

Anycast assigns same IP address to multiple servers globally; BGP routes traffic to nearest (topologically) server. Benefits: automatic geographic load balancing, DDoS resilience (distributed), reduced latency, failover without DNS propagation. Use cases: CDNs, DNS (root servers), anycast TCP (with careful session management). Challenges: TCP requires same server for connection lifetime (use connection ID or hash routing), less control than DNS-based balancing. Monitor: BGP path changes affect routing.