VPC Peering

Connecting VPCs with VPC peering

When your business or architecture becomes large enough, you will find the need to separate logical elements for security or architectural needs, or just for simplicity’s sake. 

A VPC peering connection is a one-to-one relationship between two VPCs. There can only be one peering resource between any two VPCs. You can create multiple VPC peering connections for each VPC that you own, but transitive peering relationships are not supported. You will not have any peering relationship with VPCs that your VPC is not directly peered with. You can create a VPC peering connection between your own VPCs, or with a VPC in another AWS account within a single Region.

To establish a VPC peering connection, the owner of the requester VPC (or local VPC) sends a request to the owner of the peer VPC. You or another AWS account can own the peer VPC. It cannot have a Classless Inter-Domain Routing (CIDR) block that overlaps with your requester VPC’s CIDR block. The owner of the peer VPC has to accept the VPC peering connection request to activate the VPC peering connection. 

To permit the flow of traffic between the peer VPCs using private IP addresses, add a route to one or more of your VPC’s route tables that points to the IP address range of the peer VPC. The owner of the peer VPC adds a route to one of their VPC’s route tables that points to the IP address range of your VPC. You might also need to update the security group rules that are associated with your instance to ensure that traffic to and from the peer VPC is not restricted. 

Benefits of VPC peering

Review some of the benefits of using VPC peering to connect multiple VPCs together.

• bulletBypass the internet gateway or virtual private gateway. Use VPC peering to quickly connect two or more of your networks without needing other virtual appliances in your environment.
• bulletUse highly available connections. VPC peering connections are redundant by default. AWS manages your connection.
• bulletAvoid bandwidth bottlenecks. All inter-Region traffic is encrypted with no single point of failure or bandwidth bottlenecks. Traffic always stays on the global AWS backbone, and never traverses the public internet, which reduces threats, such as common exploits, and distributed denial of service (DDoS) attacks.
• bulletUse private IP addresses to direct traffic. The VPC peering traffic remains in the private IP space.

 VPC peering for shared services

your security team provides you with a shared services VPC that each department can peer with. This VPC allows your resources to connect to a shared directory service, security scanning tools, monitoring or logging tools, and other services.

A VPC peering connection with a VPC in a different Region is present. Inter-Region VPC peering allows VPC resources that run in different AWS Regions to communicate with each other using private IP addresses. You won’t be required to use gateways, virtual private network (VPN) connections, or separate physical hardware to send traffic between your Regions.

full mesh VPC peering

each VPC must have a one-to-one connection with each VPC with which it is approved to communicate. This is because each VPC peering connection is nontransitive in nature and does not permit network traffic to pass from one peering connection to another.

The number of connections required has a direct impact on the number of potential points of failure and the requirement for monitoring. The fewer connections you need, the fewer you need to monitor and the fewer potential points of failure.

Regards

Osama