Amazon Elastic IPs and ArcGIS Server

An advantage of using Amazon EC2 is the ability to start, stop, create, and terminate instances at any time. However, this flexibility creates a potential challenge with IP addresses. Restarting a stopped instance (or re-creating an instance after another instance is terminated) results in a new IP address. How do you successfully reference a machine when the IP address is constantly changing?

In response to this problem, Amazon offers the ability to allocate an Elastic IP address. An Elastic IP provides you a single IP address that you can associate with different EC2 instances over time. If your EC2 instance has an Elastic IP and that instance is ever stopped or terminated, you can immediately associate a new EC2 instance with the Elastic IP. Your existing applications will not break because the applications see the IP address they were expecting, even though the back-end EC2 instance has changed.

If you're building your own site manually, you should associate an Elastic IP with your enterprise geodatabase instance if you have the geodatabase on its own dedicated instance. Optionally, you can also associate an Elastic IP with your ArcGIS Server instance if you are not already using an Elastic Load Balancer.

If you use ArcGIS Server Cloud Builder on Amazon Web Services to build your site, no Elastic IPs are created or needed.

If you ever need to stop an instance, you should reassociate it with its Elastic IP after you start the instance again. You can even associate the Elastic IP with a backup instance while the other instance is down. If you don't have an Elastic IP, users' connections to your machines will permanently break if you ever have to stop the instance.

Note:

An Elastic IP is not the same as an Elastic Load Balancer. An Elastic Load Balancer helps you scale out your site by associating many EC2 instances at the same time under one web address. An Elastic IP, on the other hand, can only be associated with one EC2 instance at a time.