An egress-only internet gateway is a VPC component that allows outbound communication over IPv6 from instances in your VPC to the internet, and prevents theinternet from initiating an IPv6 connection with your instances. This meets the company’s security policy and requirements. To use an egress-only internet gateway, you need to add a route in the subnet’s route table that routes IPv6 internet traffic (::/0) to the egress-only internet gateway.

Reference URLs:

1 https://docs.aws.amazon.com/vpc/latest/userguide/egress-only-internet-gateway.html

2 https://dev.to/aws-builders/what-is-an-egress-only-internet-gateways-in-aws-7gp

3 https://docs.aws.amazon.com/vpc/latest/userguide/route-table-options.html