RDS - FAQ - Does RDS support IPv6 addressing

Answer:

IPv6 is available in all regions, and IPv6 addresses can be added to both a VPC and its subnets. Amazon EC2 instances that are created in a subnet that uses IPv6 addressing have both IPv6 and IPv4 addresses.

However, RDS does not currently support IPv6. When using RDS, keep the following in mind:

• You can't associate IPv6 addresses with RDS instances, and RDS instances can't communicate with clients using IPv6. All IPv6 packets sent to RDS instances are dropped.
• You can assign IPv6 addresses to EC2 clients of RDS, but they communicate with RDS instances (as well as Read Replicas created on EC2 instances using IPv6) using IPV4 addresses.
• Amazon S3 supports IPv6, but loads to and dumps from RDS instances use IPv4.
• VPNs don't translate between IPv6 and IPv4. If you have on-premises resources that use IPv6 and communicate with RDS instances over a VPN, make sure your firewall permits communication using IPv4.