ANAME records act like a CNAME record, but at the root of your domain. Since CNAME records don’t support this functionality, we engineered our own record type that enlists the help of a network of resolving nameservers that check what IP address (IPv4 or IPv6) your hostname resolves to.
We then update your ANAME record to point to that IP address and propagate the update to all the nameservers in our network. Every time the record is queried, we’ll check the hostname again to see if the resolution has changed. That way every one of your users gets the most accurate and current response.
Unlike other providers, there is no lag in ANAME resolution because record updates are done at the time of the query rather than when TTL’s expire.
If our resolvers are unable to reach your hostname, our nameservers will return the cached IP address from an earlier query. This service also supports our GeoDNS functionality, which means each nameserver will cache the IP that resolved for that specific location.
The secret behind ANAME’s amazing accuracy is an extra piece of information that comes along with every query, called the EDNS client subnet. This information is passed along to each resolving nameserver, authoritative nameserver, and then eventually the service that the ANAME record is pointing to --usually a CDN service.
Since Constellix ANAME supports EDNS, whenever a user makes a query to an ANAME record we are able to tell where the user is located based on the EDNS client subnet. We then pass that information along to the hostname where the query will eventually resolve.
That means if you are using an ANAME record to point your domain to a CDN, all the CDN decisions will be made based on the actual locations of your end-users, rather than the location of our nameservers.