How do you assign IP address ranges to VPCs?

You assign a single Classless Internet Domain Routing (CIDR) IP address block when you create a VPC. Subnets within a VPC are addressed from this range by you. A VPC can be assigned at most one (1) IP address range at any given time; addressing a VPC from multiple IP address ranges is currently not supported. Please note that while you can create multiple VPCs with overlapping IP address ranges, doing so will prohibit you from connecting these VPCs to a common home network via the hardware VPN connection. For this reason we recommend using non-overlapping IP address ranges.  You can allocate an Amazon-provided IPv6 CIDR block to your VPC.