Anycast is a network routing technique where the same IP address is assigned to multiple servers or devices in different locations. When a user tries to connect to an anycast IP address, they're automatically routed to the nearest or best-performing server in the network.
How anycast works
Unlike traditional unicast routing (where one IP address maps to one specific server), anycast allows multiple servers to “announce” the same IP address to the internet. The network infrastructure then routes traffic to the closest available server based on network topology and routing policies.
This is particularly useful for:
- Content Delivery Networks (CDNs) like Cloudflare, AWS CloudFront, and Fastly
- DNS servers like Google's 8.8.8.8 or Cloudflare's 1.1.1.1
- Load balancing across geographically distributed servers
- DDoS mitigation by distributing attack traffic across multiple servers
Geolocation with anycast
Anycast networks present a challenge for IP geolocation because the same IP address can be served from multiple locations worldwide. They are, by definition, in multiple locations at the same time!
When you query an anycast IP address, you might get a response from New York, London, or Tokyo depending on your location and network path. These are all valid locations for the IP address.
For this reason, traditional geolocation techniques that rely on mapping IP addresses to fixed locations don't work for anycast networks.
How IPLocate handles anycast IPs
At IPLocate, when we detect that an IP address is part of an anycast network, we’ll mark this with the is_anycast field in our API response. (also available in our IP Geolocation database)
For geolocation fields, we'll provide the location of the registered network operator, or from their geofeed if they have one.
We’ll also include comprehensive ASN and company data to help you understand which organization operates the anycast network.
This way, you get accurate information about who owns and operates the IP address, as well as an indication that the IP address is part of an anycast network. You can use this to make better decisions about your application’s behavior, to better understand the network infrastructure behind an IP address, and to avoid false positives when using geolocation data for anycast networks.
Detecting anycast networks using an API
Our is_anycast field makes it easy to identify when you're dealing with an anycast IP address:
{
"ip": "8.8.8.8",
// The is_anycast field is true if the IP address is part of an
// anycast network.
"is_anycast": true,
// ...
// Location data relates to the registered network operator, not
// a specific server or user.
"country": "United States",
"country_code": "US",
"city": "Mountain View",
// ...
"asn": {
// Autonomous System data also provides information about
// the network operator. In this case, Google routes this
// anycast address.
"asn": "AS15169",
"route": "8.8.8.0/24",
"netname": "GOOGLE",
"name": "Google LLC",
"country_code": "US",
"domain": "google.com",
"type": "hosting"
},
// ...
"hosting": {
// Finally, the hosting field provides detailed information
// about the hosting provider or data center operator.
"provider": "Google Cloud",
"domain": "cloud.google.com",
"network": "8.8.8.0/24"
}
// ...
}
Learn more
Want to dive deeper into anycast? Check out these resources:
Ready to start detecting anycast networks in your applications? The is_anycast field is available on all IPLocate plans, including our free tier with 1,000 requests per day.
