What is VPC peering?
In the ever-evolving era of cloud computing, secure communication between various network environments is crucial. This is where we learn the need and importance of virtual private cloud (VPC) peering. A VPC peering connection establishes a private link between two VPCs, facilitating the secure exchange of network traffic between them. This allows instances in each VPC to interact seamlessly, as though they belong to a single cohesive network using private IP addresses. This article will dive into the fundamentals of VPC peering, its use cases, and how to set it up.
Use cases for VPC peering
VPC peering is a versatile feature with various use cases. We can establish VPC peering connections between our own VPCs, with VPCs in separate AWS accounts, or even across distinct AWS Regions.
Connecting VPCs within the same AWS account: When we have multiple VPCs within the same AWS account, we can use VPC peering to enable communication between them. This is useful for separating different application tiers or creating isolated development, testing, and production environments.
Peering VPCs in different AWS accounts: VPC peering is not limited to VPCs within the same AWS account. It can be used to connect VPCs of different AWS accounts. This is helpful for collaboration between organizations or when we want to connect with a third party’s VPC securely.
Cross-region VPC peering: AWS allows VPC peering connections between VPCs in different AWS Regions. This offers advantages regarding data recovery, data replication, or securing swift access to resources in geographically diverse locations.
Two VPCs, VPC A and VPC B, are peered together so that the traffic between the two VPCs can flow freely using private IP addresses. While peering, the routing table for VPC A keeps updating, ensuring that traffic to VPC B is routed correctly. Then, the process of requesting and accepting a VPC peering connection takes place. There is a fact that VPC peering is a decentralized operation and that each connection is independent of the others. This process brings security, isolation, and scalability between VPC’s.
Designing a VPC
While setting up VPC peering, one VPC takes on the requester’s role while the other works as a peer. Before the connection becomes active, the owner of the peer VPC must acknowledge and approve the peering request. After the connection is established, it’s necessary to configure routing within the route table for each VPC’s CIDR block. This routing setup allows resources in these network environments to communicate using their private IP address ranges.
Transitive peering
There is no transitive peering in AWS. For example, if there are three VPCs and we’ve established VPC peering between VPC A and VPC B, as well as between VPC B and VPC C, it’s important to note that this does not enable direct communication between VPC A and VPC C. To facilitate networking between these two VPCs, separate VPC peering connections must be established.
Limitations of VPC peering
The following are some limitations of VPC peering:
Each VPC can only have several active and pending VPC peering connections. This quota can be increased by contacting AWS Support.
VPC peering connections between VPCs with overlapping subnet mask ranges cannot be established. This is because traffic between peered VPCs uses private IP addresses, and overlapping CIDRs would cause routing conflicts.
VPC peering is not transitive.
VPC peering security
VPC peering offers several security benefits compared to other connectivity options, which are as follows:
Traffic between peered VPCs stays within the AWS network, avoiding disclosure to the public internet.
Security groups can be configured to define specific traffic rules between resources in the peered VPCs, allowing only authorized traffic to flow.
By limiting direct internet access for resources communicating through peering, we can shrink the potential attack surface for malicious actors.
VPCs remain isolated from each other by default. This prevents resources in one VPC from accessing resources in the other.
VPC endpoints can access AWS services without needing an internet gateway, which enhances security.
Conclusion
VPC peering is a fundamental feature for building complex and interconnected cloud infrastructures. It empowers AWS users to create secure and private connections between VPCs.
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