Amazon Elastic IPs and ArcGIS Server

An advantage of using the Amazon cloud 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) creates 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 create an Elastic IP. 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 Elastic IP they were expecting, even though the back-end EC2 instance has changed.

It's important to set up an Elastic IP for EC2 instances containing ArcSDE. If you ever need to stop your instance, all you have to do is reassociate that instance with the Elastic IP after you restart the instance. 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 geodatabase 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 ArcGIS Server deployment 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.