IP changed when EC2 instance stopped and started

I have a strange issue here regarding and EC2 instance. I had just stopped and started an EC2 instance for windows after expanding the boot drive, not after I had started the instance, the IP it was assigned prior to the stop-start phase, has now changed to a new IP. Anyone has had a similar issue or is it usual in a stop-start scenario?

Any time you start/stop an EC2 instance, what you're really doing is turning on an entirely new virtual server. Which means it gets a new IP address each time.

Luckily for you, Amazon offers Elastic IPs for EC2 instances so you can have a fixed permanent IP that you can assign to any of your instances (and change which instance uses it anytime you like). A little more info can be found on their IP address FAQ for EC2: http://docs.amazonwebservices.com/AWSEC2/latest/DeveloperGuide/index.html?IP_Information.html

And probably lots more in rest of their documentation: http://aws.amazon.com/documentation/ec2/

Especially the Developer Guide: http://docs.amazonwebservices.com/AWSEC2/latest/DeveloperGuide/

Stop/start for Windows (shutdown) will assign a new public/private IP to the instance. If you need a guaranteed public IP then you need to use an Elastic IP.