Security admin is not allowing to open a blanket allowance for “*.amazonaws.com” as per mentioned in the docs (note that this is the NY reference - we are on London at present but in upgrade planning). https://docs.servicenow.com/bundle/newyork-it-operations-management/page/product/cloud-management-v2-setup/task/aws-setup-mid-server-cloud-mgt.html

List of exact url that we need to whitelist to run the AWS Cloud Discovery.

Please use the list in below AWS documentation for service endpoints.
https://docs.aws.amazon.com/general/latest/gr/ec2-service.html

I have attached "aws-general.pdf" (downloaded from https://docs.aws.amazon.com/general/latest/gr/rande.html) and you can refer to the same information at page 125.

There's one more URL to add:
https://ec2.amazonaws.com

This should cover the URLs that AWS cloud discovery need.

Amazon Documentation:

https://docs.aws.amazon.com/general/latest/gr/rande.html

https://docs.aws.amazon.com/general/latest/gr/aws-service-information.html

https://docs.aws.amazon.com/general/latest/gr/ec2-service.html