Anycast is a design, not a checkbox

Anycast means the same IP prefix is announced from several places at once, and BGP steers each user toward a nearby healthy site. It is a network design with shared addressing, careful health checks, and an application that can survive a site going quiet. It is not a checkbox you tick when you order two VPS guests in two cities. We only treat a product as anycast when the product description says so. Two cities of inventory simply means two places you can place a server.

What anycast actually does

With anycast, one address such as 192.0.2.1 (or a matching IPv6 prefix) is advertised from more than one city. The internet picks the best path for each client. Someone near Frankfurt usually lands in Frankfurt. If that site fails and you withdraw the route cleanly, other sites can take the traffic. Sessions, mail queues, and admin logins still need a plan, or failover will look fine on paper and break in practice. A CMS with one database in one city is not ready for anycast even if the IPs are.

DNS failover is a different tool

Two A records, a short TTL, and two VPS guests is DNS failover. Resolvers choose one address and often keep it until the TTL expires. Some visitors can stay pointed at a dead city for that whole window. Health-checked DNS that removes a bad address is the more careful version of the same idea. It is honest and often enough for a simple site. It is still not anycast, and calling it anycast in a ticket only confuses provisioning.

Match the app to the failover plan

Global static files usually belong on a CDN. If you need “when New York fails, use London,” say DNS failover or CDN in the first sentence so we provision the right thing. Same IP from many cities with BGP is anycast, and it is a project. The app has to tolerate the move. State that lives in one city does not magically follow the route.

dig example.com A +short

Two addresses in that answer means two addresses, not anycast. A looking-glass view of the same prefix from two cities points toward anycast (or a route leak). Those pastes help us see which design you meant. Name anycast, DNS failover, or CDN up front. If you already announce one prefix from two places, include a looking-glass paste as well. The rest of the internet will show which design you actually built.