You can use Express Connect to achieve private-network communication between two VPCs. Express Connect can avoid the network instability caused by bypassing the public network and eliminate the risk of data theft during transmission. For more information, see Establish an intranet connection between VPCs in different regions and Establish an intranet connection between VPCs under different acounts.
If your on-premises IDC needs to communicate with a VPC through a private network, you can use the physical connection function of Express Connect to implement private-network communication on both sides. You can build a physical connection by yourself or contact an Alibaba partner to help you build a physical connection. The communication between the on-premises IDC and the VPC by using the physical connection features high quality, high reliability, and high security. For more information, see Access a VPC under the same account through a physical connection and Access a VPC under a different account through a physical connection.
If two VPCs need to use the same NAT gateway to access a public network, you can also use Express Connect.