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I wanted to create a new EC2 instance that was identical to one that we already have running. After creating the instance, I noticed that it could not be accessed from the outside. First, these are the steps I followed.

  • Select existing EC2 instance > Image menu > Create image
  • Once the image is created, navigate to the Images section on the left panel > AMI's > Select new image and Launch > proceed with default settings > New instance is created.
  • Finally, assign an ElasticIP to the new Instance > configure DNS (separate provider) > configure the incoming Security policy for the instance back on AWS.

I was able to start the instance, RDP in (its Windows) using the same password of the old instance, install the required software, completely TURN OFF windows firewall (for debugging).

And yet, I cannot access the new instance from the outside.

I know the DNS is successfully resolving to the elastic IP (this is proven when I try to ping the URL), but I cannot access any of the application ports via the Amazon public DNS, my domain, or the elastic IP.

One more thing I noticed is that the hostname of the new instance and old instance are identical (as shown on the Windows desktop). The new instance is also missing some other things that are shown in the old instance. Any ideas?

new Instance old Instance with same hostname

john
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  • Side-note: When creating an AMI of a Windows instance, it is a good idea to run `sysprep` to change the unique identities that Windows assigns. See [Use Sysprep to Create and Install Custom Reusable Windows AMIs](https://aws.amazon.com/premiumsupport/knowledge-center/sysprep-create-install-ec2-windows-amis/) and also see [Create a Standard Amazon Machine Image Using Sysprep - Amazon Elastic Compute Cloud](https://docs.aws.amazon.com/AWSEC2/latest/WindowsGuide/ami-create-standard.html). – John Rotenstein Mar 25 '20 at 04:36
  • The fact that you can RDP into the new instance, but not access particular applications, suggests that the Security Group is not allowing the connections or the applications are not running on the instance. You could try connecting to the application ports from the instance itself (eg `localhost:8080` or whatever port is being used). This will test whether the application is running. – John Rotenstein Mar 25 '20 at 04:39
  • @JohnRotenstein the application is running indeed (accessible from the inside the instance). And the security policies in both instances are identical, but the old one works while the new one does not. And thanks for the links, I'll check them out. – john Mar 25 '20 at 10:54

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