Question

A company runs a production VPC (10.20.0.0/16) in us-east-1 that hosts a large containerized workload. IP address exhaustion is occurring because the primary CIDR is nearly fully allocated across existing subnets, and the platform team needs additional address space for new subnets to support cluster scaling. RFC 1918 space in the 10.0.0.0/8 range is heavily used by other VPCs and on-premises networks, but the 100.64.0.0/10 shared address space is available. Existing workloads, Transit Gateway attachments, and routing must remain uninterrupted. What is the most appropriate way to expand the VPC's usable address space?

Accepted Answer

Associate a secondary CIDR block from the 100.64.0.0/10 range with the existing VPC and create new subnets from that block for the additional workloads.

Answer

Modify the primary CIDR block of the VPC to a larger prefix such as 10.20.0.0/15 to double the available address space in place.

Answer

Create a new VPC using the 100.64.0.0/10 range, then establish VPC peering and migrate all existing workloads into the new VPC.

Answer

Delete underused subnets and recreate them with smaller prefixes to reclaim address space within the existing 10.20.0.0/16 block.