Transit Gateway

aws/networking aws/vpc

💡 Definition

AWS Transit Gateway connects VPCs and on-premises networks through a central hub. It simplifies your network and puts an end to complex peering relationships.

🔑 Key Concepts

Hub and Spoke: Acts as a central cloud router. All VPCs and on-prem connections attach to the Transit Gateway.
Simplification: Replaces full-mesh VPC Peering (where every VPC connects to every other VPC).
Transitive Routing: Allows traffic to flow from A to B to C (unlike VPC Peering).
Multicast: Supports IP multicast.

⚙️ How it Works

You create a Transit Gateway and attach your VPCs, VPNs, and Direct Connect gateways to it. You then update route tables to send traffic destined for other networks to the Transit Gateway.

🎯 Use Cases

Large Scale Networking: Connecting hundreds or thousands of VPCs.
Hybrid Cloud: Centralizing connectivity from on-premises to multiple VPCs.
Network Segmentation: Using route tables to control which VPCs can talk to each other.

💰 Pricing Model

Attachments: Charged per hour per attachment.
Data Processing: Charged per GB of data processed.

📝 Exam Tips (CLF-C02)

Think "Hub" or "Cloud Router".
Solves the complexity of many-to-many VPC connections.
Supports transitive peering (A can talk to C via B).

See Also: * VPC Peering * VPN * Direct Connect