Restrict Access to Your Elastic Beanstalk Domain While Using an ALB

All those IPs are valid, but they're not Elastic IPs, so they can't be used to route traffic directly to the public internet. To access the internet, you'll need a NAT Gateway or an instance with an Elastic IP. While you can choose any IP range, I as well recommend using RFC 1918 ranges for internal IPs. Its also stated in the documentation Leo shared: We refer to private IP addresses as the IP addresses that are within the IPv4 CIDR range of the VPC. Most VPC IP address ranges fall within the private (non-publicly routable) IP address ranges specified in RFC 1918; however, you can use publicly routable CIDR blocks for your VPC. Regardless of the IP address range of your VPC, we do not support direct access to the internet from your VPC's CIDR block, including a publicly-routable CIDR block. You must set up internet access through a gateway; for example, an internet gateway, virtual private gateway, a AWS Site-to-Site VPN connection, or AWS Direct Connect.

That's only half the story. When you use public IP addresses belonging to someone else in your VPC, those same IPs will be permitted on the public internet and accepted as such by AWS's services. IP address restrictions, addresses reflected in logs, and so on will consider the public IP addresses as valid when used by their legitimate holder, whenever they appear outside the VPC where they are configured as local. Also, using someone else's IPs as internal ones effectively prevents them from connecting to resources inside the VPC, so it is not correct to consider such use as "valid".

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