Whitelist Domain Name

Is there a way to whitelist a domain name/hostname instead of an IP address? We have an EC2 instance for QA passes that is spun up only when we need to deploy code. It has no static IP address and the public DNS name changes each time the instance gets created at Amazon. When we try to run Behat features to test the Admin/Login pages we get blocked immediately. We have several hundred sites and it is not practical to whitelist the IP on each of them.

DNS resolves through a Route53 hosted zone with a CNAME that points the domain name in question to the EC2 instance’s public DNS name, for example, ec2-203-0-113-25.compute-1.amazonaws.com.

Any insight would be helpful.