Public IP been changed after I reboot my EC2

Surely this is the default behaviour of EC2 unless you allocate (and pay for) a fixed public IP address, isn't it? There is lots of documentation around on how to use a DDNS service to overcome this. As I understand it, each running EC2 instance gets a public IP address allocated when it is booted up and this remains allocated until the instance is shut down at which point it may get harvested. If you intend to keep the instance running 24/7, you can get a public IP address permanently allocated to it, but you will pay a small standing charge for that address if the instance that it is allocated to is not running.

Maby is correct. Amazon allocates a public IP address until the instances has been shut down and brought back up.

You can look into getting an Elastic IP and associating it with whatever instance you'd like if maintaining the IP address is an issue. Either that or keeping the machine on.

One thing to note: Elastic IP's are free under the trial as long as the machine is on.

Depending on your application, DDNS may be an acceptable solution. I'm running an EC2 instance intermittently during development and testing and didn't want to have to reconfigure each client everytime I start the VM - I registered with one of the free DDNS services and configured the VM to refresh the records each time it start - apart from a lag of a few seconds on each reboot, it works well.
Given that this must be a fairly common requirement, I'm surprised that Amazon have not included DDNS functionality in Route53...

Edited by: Maby on Sep 11, 2017 11:07 PM

Thanks for kindly help.