What is an anycast IP address?

Q: Why is anycast used?

Anycast gives three big wins: speed (users hit a nearby server, cutting latency), resilience (if one location fails, routing shifts traffic to the next-nearest automatically), and DDoS absorption (an attack gets spread across many sites instead of overwhelming one). It’s why CDNs, public DNS resolvers, and large services rely on it.

Quick answer

Some IP addresses seem to be in many places at once — 1.1.1.1 and 8.8.8.8 answer from a server near you whether you’re in Mumbai or Munich. That’s anycast, the routing trick behind CDNs and global DNS. Here’s how it works.

The core idea

Normally one IP maps to one server in one place (unicast). With anycast, the same IP is announced from many locations worldwide simultaneously. Internet routing then delivers each user’s request to the nearest announcement — the closest server — automatically. One address, many servers, each user reaching whichever is closest.

How routing picks the nearest

The internet’s routing protocol (BGP) sees multiple paths to the same anycast IP and chooses the shortest for each user. So a request to 1.1.1.1 from India lands on a nearby node, while the same address from Germany lands on a European node — no special client logic needed. The network does the steering.

Why is anycast used?

Anycast gives three big wins: speed (users hit a nearby server, cutting latency), resilience (if one location fails, routing shifts traffic to the next-nearest automatically), and DDoS absorption (an attack gets spread across many sites instead of overwhelming one). It’s why CDNs, public DNS resolvers, and large services rely on it.

Why does anycast break geolocation?

Anycast is a key reason IP geolocation can be wrong. A single anycast IP genuinely exists in dozens of cities, so a geolocation database can’t pin it to one place — it may report the provider’s headquarters or a default location. If you look up an anycast address like 8.8.8.8, expect an approximate or generic result, not a real city.

Seeing it in practice

Look up a known anycast IP (1.1.1.1, 8.8.8.8) with our Bulk IP Audit tool — you’ll see the network owner (Cloudflare, Google) but a location that doesn’t reflect where you’re actually being served from. That gap between “one IP” and “many servers” is anycast working as intended.