Introduction

VPC Peering is a networking service that allows the connection of two Virtual Private Clouds (VPCs) within the same or different AWS regions, enabling traffic between them without the need for internet gateways, VPNs, or physical hardware. This connection allows resources in different VPCs to communicate as if they were in the same network, providing a flexible and secure method for expanding cloud infrastructure. VPC Peering is commonly used to interconnect environments, enable service sharing, or create multi-region architectures.

Key Features

  1. Private Communication: Traffic between peered VPCs stays within the AWS backbone, ensuring low latency and high security. It does not traverse the public internet.
  2. Multi-Region Peering: AWS supports peering across different regions, enabling global, cross-region connectivity.
  3. No Single Point of Failure: VPC Peering is fully redundant within the AWS backbone, providing a reliable connection.
  4. Route Tables Control: You can manage traffic between VPCs by configuring route tables, giving you fine-grained control over what resources in one VPC can access in the other.
  5. No Bandwidth Bottleneck: Peered VPCs enjoy the same bandwidth capabilities as standard traffic within AWS, meaning there are no inherent bottlenecks imposed by VPC Peering itself.
  6. Does not support for Transitive Peering Directly: VPC Peering doesn’t support direct transitive routing; however, routes can be configured between multiple VPCs using additional peerings to form complex architectures.

Limitations and Challenges

  1. No Transitive Routing: VPC Peering connections are non-transitive, meaning that if VPC A is peered with VPC B, and VPC B is peered with VPC C, VPC A cannot directly communicate with VPC C. Each connection requires explicit configuration.
  2. Route Table Complexity: As the number of peered VPCs increases, managing route tables can become complex, particularly in environments with multiple VPCs across regions.
  3. No Overlapping IP Addresses: VPCs must have non-overlapping CIDR blocks for peering to work. Overlapping ranges will cause the peering request to fail.
  4. VPC Peering Costs: While there’s no charge for creating a VPC Peering connection, data transfer costs still apply. This can become costly if significant data is transferred across peered VPCs, especially in multi-region setups.

Common Use Cases

  1. Service Segmentation: VPC Peering can be used to segment environments such as development, staging, and production into separate VPCs while still allowing communication between them when necessary.
  2. Cross-Region Applications: Applications distributed across multiple AWS regions can use VPC Peering to maintain low-latency connections between the different parts of the application.
  3. Resource Sharing: One VPC might host shared resources such as databases, storage, or security services, and VPC Peering can provide other VPCs access to these resources without exposing them to the public internet.
  4. Business Mergers or Collaboration: If two companies, teams, or divisions are using separate VPCs for their AWS workloads, VPC Peering allows them to securely connect these environments without major reconfigurations.