In this section, we will look at the various methods of connecting multiple VPCs. A customer can have multiple VPCs for various reasons: security, billing, needing cloud infrastructure in more than one region, and so on. 

When using multiple VPCs and planning to connect them to one another, the users must ensure that there are no overlapping IPs between any of the VPCs. Hence, it is important for the user to plan the IP allocation right at the beginning, and assign a contiguous CIDR range for each VPC.

We can connect VPCs using the following techniques:

• VPC peering
• Hardware VPN
• Software VPN
• Software-to-hardware VPN
• Direct Connect

Let's look at each of these in detail