VPC Peering Essentials:
- VPC peering is used to extend your private network from one VPC, or one subnet, or specifically one instance, to another VPC.
- This is for sharing internal resources, via private IP addresses.
- VPC peering can only occur between two VPCs that are in the same region.
- You cannot configure VPC peering between VPCs in two different regions.
- You can however configure VPC peering between VPCs in different accounts - but only if they are in the same region.
- To peer VPCs, they must have separate (non-overlapping) CIDR block ranges.
- Transitive connections are not allowed.
- You can configure the peering to connect the entire VPC, or just specific subnets.