Understanding IPv6 Support in AWS VPC

Amazon Virtual Private Cloud (VPC) supports IPv6, allowing you to run your resources in a dual-stack mode. This means your resources can communicate over both IPv4 and IPv6, independently of each other. Here’s a detailed look at how you can integrate IPv6 support into your existing VPC and the considerations to keep in mind.

Adding IPv6 Support to Your VPC
If you have an existing VPC that supports only IPv4, you can add IPv6 support to it. This allows your resources to communicate over both IPv4 and IPv6. However, it’s important to note that you cannot disable IPv4 support for your VPC and subnets, as IPv4 is the default IP addressing system for Amazon VPC and Amazon EC2.

Key Considerations

• No Migration Path: There is no migration path from IPv4-only subnets to IPv6-only subnets. You will need to configure your subnets to support both IPv4 and IPv6.
• VPC and Subnet Configuration: This guide assumes you have an existing VPC with public and private subnets. For creating a new VPC with IPv6 support, refer to the AWS documentation on creating a VPC.

IPv6 VPC CIDR Blocks
You can associate a single IPv6 CIDR block when creating a new VPC or up to five IPv6 CIDR blocks from /44 to /60 in increments of /4. These blocks can be requested from Amazon’s pool of IPv6 addresses. For more details, see the AWS documentation on adding or removing a CIDR block from your VPC.

• Example: When you create a VPC and specify an Amazon-provided IPv6 CIDR block, Amazon assigns a block like 2001:db8:1234:1a00::/56. You can then create subnets and associate IPv6 CIDR blocks from this range, such as 2001:db8:1234:1a00::/64.

Disassociating IPv6 CIDR Blocks
You can disassociate an IPv6 CIDR block from a VPC. However, once disassociated, you cannot expect to receive the same CIDR block if you associate an IPv6 CIDR block with your VPC again later.

Characteristics of IPv6 in AWS VPC

• VPC Size: Up to 5 CIDRs from /44 to /60 in increments of /4. This quota is adjustable.
• Subnet Size: From /44 to /64 in increments of /4.
• Address Selection: You can bring your own IPv6 CIDR block, choose an Amazon-provided block, or allocate a block from Amazon VPC IP Address Manager (IPAM).
• Internet Access: Requires an internet gateway. Supports outbound-only communication using an egress-only internet gateway.
• Elastic IP Addresses: Not supported. IPv6 addresses are static by default.
• NAT Gateways: Supported. You can use a NAT gateway with NAT64 to enable instances in IPv6-only subnets to communicate with IPv4-only resources.
• DNS Names: Instances receive Amazon-provided IPBN or RBN-based DNS names, resolving to the DNS records selected for the instance.

Best Practices for IPv6 Implementation

1. Analyze Your Use Case: Evaluate your specific requirements and use cases for transitioning to IPv6.
2. Assess IPv6 Readiness: Conduct an audit and inventory of your network infrastructure to ensure it supports IPv6.
3. Training IT Staff: Ensure your IT staff is well-trained on IPv6 concepts and configurations.
4. Choose Your Transition Strategy: Decide on a transition strategy that suits your organization, such as dual-stack, tunneling, or translation.
5. Design Your IPv6 Network: Create a detailed technical plan for IPv6 deployment, considering all aspects of your environment.
6. Testing Phase: Implement a pilot deployment to test IPv6 functionality and address any issues before full-scale deployment.
7. Gradual Deployment: Deploy IPv6 in gradual shifts rather than a big-bang approach to minimize disruptions.

Conclusion
Integrating IPv6 support into your AWS VPC allows for greater flexibility and future-proofing your network infrastructure. By understanding the key considerations, characteristics, and best practices for IPv6 implementation, you can effectively manage and utilize both IPv4 and IPv6 within your VPC.