AWS Direct Connect (DX) uses three types of virtual interfaces (VIFs)—Public, Private, and Transit—to connect your on-premises network to different AWS resources. The key difference lies in the type of AWS resources they can access and how they are associated within AWS.
- Purpose: Access public AWS services (S3, DynamoDB, public EC2) using public IP addresses.
- How it Works: Provides a private path to AWS public endpoints, avoiding the public internet but using public IP space.
- Use Case: Connecting to services like S3 or DynamoDB from on-premises without traversing the internet.
- Purpose: Securely access your private resources within one or more Amazon VPCs using private IP addresses.
- How it Works: Connects to a Virtual Private Gateway (VGW) for a single VPC, or a Direct Connect Gateway for multiple VPCs/accounts, ensuring traffic stays private.
- Use Case: Connecting on-premises servers to databases or application servers in your VPCs.
- Purpose: Connect your network to one or more AWS Transit Gateways associated with a Direct Connect Gateway, enabling centralized network management.
- How it Works: Acts as the link between your physical network and the Transit Gateway, allowing you to route traffic to many VPCs through that single point.
- Use Case: Scaling connectivity across many VPCs and accounts, replacing numerous Private VIFs, especially for larger hybrid cloud environments.
Key Differences Summary
- Public VIF: Public IPs, Public AWS Services.
- Private VIF: Private IPs, Your VPC resources (single or few).
- Transit VIF: Private IPs, Transit Gateway (many VPCs/accounts).
| Feature | Public VIF | Private VIF | Transit VIF |
| AWS Resources Accessed | All AWS public services (e.g., Amazon S3, DynamoDB, public EC2 IPs) globally using public IP addresses. | Resources within your Amazon VPC using private IP addresses (e.g., EC2 instances, RDS). | Resources attached to one or more AWS Transit Gateways across multiple regions using private IP addresses. |
| Connectivity | Connects to the public AWS network edge, bypassing the internet. | Connects to a Virtual Private Gateway (VGW) or a Direct Connect Gateway (DXGW). | Connects to a Direct Connect Gateway (DXGW), which is then associated with an AWS Transit Gateway. |
| Gateway Requirement | No gateway needed. | Requires a VGW (for single VPC in same region) or a DXGW (for multiple VPCs/regions). | Requires a DXGW. |
| IP Addressing | Uses public IP addresses and requires a public ASN. | Uses private IP addresses. | Uses private IP addresses. |
| Scalability | Accesses public services globally. | Suited for smaller, single VPC setups or limited multi-VPC scenarios via DXGW. | Ideal for large-scale, multi-VPC, multi-account, and multi-region hub-and-spoke architectures. |
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