Need to know the dynamic IP ranges used by AWS in a specific region? AWS publishes this as a JSON file.
curl -s https://ip-ranges.amazonaws.com/ip-ranges.json | jq '.prefixes | .[] | select((.region == "eu-west-1") and (.service == "EC2")) | .ip_prefix' | sed 's/"//g'
This filters for EC2 in eu-west-1 (Ireland) and outputs CIDR blocks.
To check another service:
curl -s https://ip-ranges.amazonaws.com/ip-ranges.json | jq '.prefixes | .[] | select(.service == "CLOUDFRONT") | .ip_prefix' | sed 's/"//g'
Useful for firewall rules.
Enjoy!