The resource record sets contained in a hosted zone must share the same suffix. For example, theexample.com hosted zone can contain resource record sets for www.example.com andwww.aws.example.com subdomains, but it cannot contain resource record sets for awww.example.ca subdomain. Reference: http://docs.aws.amazon.com/Route53/latest/DeveloperGuide/AboutHosedZones.html