Looking for a "best practice" answer to managing externally-addressable hosts using the combination of Amazon EC2 and Amazon Route 53, without using Elastic IPs for each host. In my scenario I will have 30+ hosts that need to be accessible from outside EC2, so directly using internal DNS will not work.

In the past, I have addressed hosts by assigning an elastic IP to that host (let's say, 55.55.55.55) and then creating an associated A record. For example, let's say I want to create "ec2-corp01.mydomain.com" I might do:

ec2-corp01.mydomain.com.     A     55.55.55.55     300

Then on that EC2 instance, I would assign the Elastic IP of 55.55.55.55, and everything works fine. Of course, to make this work, I need to have one Elastic IP per instance, which is something I'd like to avoid if possible; I'd like the infrastructure to be more dynamic.

So my thought is to try something like:

• Create a script that queries the internal EC2 tools to determine an instance's private hostname

• On instance boot, call that script to determine its hostname, and then using the command-line Route 53 interface to find and update that hostname to its current internal hostname

• Since the host will have a relatively low TTL (let's say 300 as above, or 5 minutes) it should take effect pretty quickly

Is this a good idea? Is there a better or more widely accepted way to handle it?

If it IS a good idea, what type of record should I be creating? A CNAME that points to the internal host, like ec2-55-55-55-55.compute-1.amazonaws.com? Is an A record better or worse?

Thanks!