# VPC Peering

* A VPC peering connection is a **networking connection between two VPCs that enables you to route traffic between them using private IPv4 addresses or IPv6 addresses**.\

* Instances in either VPC can **communicate with each other as if they are within the same network**.\

* The **VPCs can be in different regions and different accounts**.\

* To send private IPv4 traffic from your instance to an instance in a peer VPC, you **must add a route to the route table that's associated with your subnet in which your instance resides**.
  * The **route points to the CIDR block of the peer VPC** in the VPC peering connection, and **specifies the VPC peering connection as the target**.

## Transitive peering

* Instead of using VPC peering, you can **use an AWS Transit Gateway that acts as a network transit hub**, to interconnect your VPCs and on-premises networks.\

* You have a **VPC peering connection between VPC A and VPC B, and between VPC A and VPC C**. \

* There is **no VPC peering connection between VPC B and VPC C**.
  * So, you **cannot route packets directly from VPC B to VPC C through VPC A**.

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