I have *.example.com Route 53 alias record which pointed to distribution1.cloudfront.net. Distribution1 has static.example.com as alternative name. So far so good – it’s standard DNS behavior.
I created another CF distribution – distribution2.cloudfront.net, with dynamic.example.com alternative name.
And, without adding dynamic.example.com DNS record, which points to the second distribution, web requests to dynamic.example.com are going to distribution2.cloudfront.net, not according to DNS.
I.e., ‘nslookup dynamic.example.com’ returns distribution1.cloudfront.net IPs, but HTTP request – objects from distribution2.cloudfront.net.
It’s definitely a feature, but
- I’d like to understand how it’s implemented technically
- I already RTFM, but couldn’t see any documentation regarding this
It is documented behaviour, though somewhat hidden in the fine print:
[Y]ou can add a wildcard alternate domain name, such as
*.example.com, that includes (that overlaps with) a non-wildcard alternate domain name, such aswww.example.com. If you have overlapping alternate domain names in two distributions, CloudFront sends the request to the distribution with the more specific name match, regardless of the distribution that the DNS record points to. For example,marketing.domain.comis more specific than*.domain.com.https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/CNAMEs.html#alternate-domain-names-restrictions
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