Posted On: Nov 16, 2023

Amazon VPC allows customers to create VPCs and subnets of different sizes using IPv6 CIDRs. With this capability, customers can now create VPCs in sizes between /44 and /60, and subnets in sizes between /44 and /64, in increments of /4. Before today, AWS supported one standard IPv6 CIDR block size of /56 for VPC and /64 for subnet, whereas IPv4 CIDR block size were flexible for both VPCs and subnets.

Customers require VPCs of different sizes for growth planning, and can use a single contiguous CIDR block across thousands of smaller (E.g., /60) VPCs to optimize CIDR allocations. Alternatively, customers that want to match on-premise network designs of a logical network can create a large (E.g., /44) VPC and have a subnet of the same size in it.

VPCs and subnets of different sizes using IPv6 CIDRs is now available in all AWS commercial regions and AWS GovCloud (US) regions. For more information, please visit the VPC documentation page.