Using Elastic IP to Identify Internal Instances on Amazon EC2 · Alestic.com - A Personal AWS Blog by Eric Hammond

Elastic IP Amazon EC2 supports Elastic IP Addresses to implement the effect of having a static IP address for public servers running on EC2. You can point the Elastic IP at any of your EC2 instances, changing the active instance at any time, without changing the IP address seen by the public outside of EC2. This is a valuable feature for things like web and email servers, especially if you need to

[ionis]

route53にEIPを設定するとプライベートIPで返ってくるから、課金には優しいけど、意図せず繋がらなくなる場合もある的な話かな～。

[aquarla]

"Elastic IP の AWSから割り当てられる外部DNS名も、EC2内部でひけば、private IP address がかえってくるので、必ず同一の Elastic IP を割り当てるのなら、簡単にインスタンス間でひも付けができる。 "