既有的 Amazon VPC 可以增加更多的 subnet 了：「Amazon Virtual Private Cloud (VPC) now allows customers to expand their existing VPCs」。
Amazon Virtual Private Cloud (VPC) now allows customers to expand their VPCs by adding secondary IPv4 address ranges (CIDRs) to their VPCs.
除了中國與 GovCloud 以外都支援了：
There is no additional charge to use this feature. This feature is available in all AWS regions except GovCloud and AWS China (Beijing) regions.
這樣就不用另外開一個 VPC 再用 peering 的方式打通...