Are BYOIPs available to subaccounts?

Good question. The only way to do this today is to use Amazon's VPC IP Address Manager (IPAM) and integrate IPAM with AWS Organizations.

Then you can specify an "IPAM admin" account and share those IPAM pools with other accounts in the organization: https://docs.aws.amazon.com/vpc/latest/ipam/enable-integ-ipam.html

My understanding is that Yes, you can make them available to other accounts transferring those EIP from account A to B as need it after the IPs have been imported to AWS. The link in the comment from: AWS rePost-User-6344919 shows you how to do it: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/elastic-ip-addresses-eip.html If you want to have a service that allows you to share IP address space across AWS accounts, you need to use IPAM. Without using IPAM, you cannot share your public IP space across AWS Organizations accounts; you will have to do the transfer of EIP everytime. https://docs.aws.amazon.com/vpc/latest/ipam/tutorials-byoip-ipam.html

Yes, we can use BYOIP IP addresses as Elastic IP’s to a sub account, but there are limitations. Firstly, the BYOIP process should be completed in the master account of AWS organizations. However, if we are in the same AWS Organization as the master account and the sub account has the necessary IAM Permissions, we can associate our own IP with an Elastic IP. Additionally, from documentation 1, “An Elastic IP address can come from a custom IPv4 address pool that you have brought into you AWS Account.” There are limits on the regions of the BYOIP feature, as it is not available in the China Regions.

Refer to docs 1 and 2 for further information on detailed steps.

Doc 1: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/elastic-ip-addresses-eip.html Doc 2: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-byoip.html