How to Document AWS Transit Gateway and Direct Connect Architecture

🔗 The Core Architecture: What to Document

The central element to document is the data flow path. The standard, scalable architecture is a chain of connections:

On-premises → Direct Connect → Transit VIF → Direct Connect Gateway → Transit Gateway → VPCs

Here are the essential components to include in your diagram:

• On-Premises Network: Your corporate data center, including its IP address space (e.g., 192.168.0.0/16) and your Customer Gateway (the router on your side).
• AWS Direct Connect: The dedicated physical connection. Document its type: Dedicated Connection (direct to AWS) or Hosted Connection (via a partner).
• Direct Connect Location: The specific AWS facility or partner location where the physical connection terminates.
• Transit Virtual Interface (Transit VIF): This is the key logical interface on the AWS side of your Direct Connect connection. It's the entry point into the AWS network.
• Direct Connect Gateway (DXGW): A global AWS resource that acts as the bridge between your Transit VIF and your Transit Gateway(s).
• Transit Gateway (TGW): The central "hub" router that connects all of your VPCs, VPNs, and the Direct Connect connection.
• VPC Attachments: Each VPC (and its subnets) that is attached to the Transit Gateway. Show the VPCs as "spokes" connected to the central hub.
• Route Tables: Transit Gateway route tables are crucial. They control how traffic is routed between the different attachments (e.g., from the DXGW attachment to the VPC attachments).
• VPN (Optional): If you have a Site-to-Site VPN as a backup or secondary path, include it in your diagram.

📝 Best Practices for Your Documentation

1. Use Official AWS Icons: Always use the official AWS Architecture Icons to ensure your diagrams are professional and easily understood.
2. Show the Full Path: Ensure the diagram clearly illustrates the end-to-end connectivity from the on-premises data center to the VPC subnets.
3. Label Key Resources and IP Spaces: Every component should be clearly labeled. Crucially, include the CIDR blocks for your on-premises network and your VPCs to show routing context.
4. Show Route Advertisement: Document how routes are advertised. For example, you can indicate that the Direct Connect Gateway advertises prefixes from AWS to your on-premises network and vice versa.
5. Specify Virtual Interfaces (VIFs): Clearly distinguish between different virtual interfaces. A Transit VIF connects to a Transit Gateway via a Direct Connect Gateway, while a Private VIF connects to a single VPC.
6. Document the AWS Account Structure: In a multi-account setup, your Direct Connect and Transit Gateway often reside in a dedicated networking account. Show this boundary in your documentation to clarify ownership and management.
7. Highlight Redundancy: If you have a resilient setup with multiple Direct Connect connections or a VPN backup, make this clear. The Maximum Resiliency model, for instance, uses dedicated connections to achieve a 99.99% SLA.
8. Incorporate Operational Data: Where possible, add key details like bandwidth (e.g., "1.25 Gbps per VPN tunnel"), BGP AS numbers, and route limits.

🛠️ Tools to Create Your Diagrams

• AI Line Studio: You can describe the architecture you need in plain English. For example, a prompt like "an architecture with an on-premises data center connected via Direct Connect to a Transit Gateway with VPC attachments" will generate a structured diagram in seconds. It uses 3,000+ officially licensed icons across AWS, Azure, GCP, and OCI. Get started with the AWS diagram generator, the cloud architecture diagram tool, the AI cloud diagram generator, or the AI system architecture generator.
• AWS Official Documentation: AWS provides excellent, editable reference diagrams that you can use as a starting point. For instance, the "Traffic Segmentation Options in AWS Direct Connect" guide includes downloadable diagrams.
• Manual Diagramming Tools: For more control, you can use tools like draw.io or Lucidchart, which have built-in AWS shape libraries. Many of the official AWS reference diagrams are available in these formats.