Transit VPC VS Transit Gateway

While you can use a Transit VPC (also known as a hub-and-spoke VPC), Transit Gateway is generally the recommended modern approach. Here's why:

Transit VPC Approach:

• Requires running and managing EC2 instances as software routers/VPN endpoints

• More complex to maintain and scale

• Higher operational overhead (patching, updates, monitoring)

• More expensive due to EC2 instance costs

• Limited bandwidth based on EC2 instance types

• Requires manual route table management

• More complex network architecture

Transit Gateway Benefits:

• Fully managed AWS service

• Simpler architecture and easier to maintain

• Automatic scaling without managing infrastructure

• Support for thousands of VPCs

• Higher bandwidth (up to 50 Gbps per VPC connection)

• Centralized route management

• Built-in monitoring and metrics

• Support for multiple routing tables

• Direct Connect integration

• Multicast support

• Inter-region peering capability

The main reason to still consider Transit VPC would be:

• If you have specific routing requirements that Transit Gateway doesn't support

• If you need complete control over the routing infrastructure

• If you're heavily invested in an existing Transit VPC setup that works well

However, for new implementations, Transit Gateway is almost always the better choice due to its simplicity, scalability, and lower operational overhead.

You can use AWS Transit Gateway to connect to third-party cloud providers through several methods:

1. Site-to-Site VPN:

• Set up a VPN connection between Transit Gateway and the third-party cloud

• Supports IPsec VPN connections

• Can connect to providers like:

  • Google Cloud Platform (GCP)

  • Microsoft Azure

  • Oracle Cloud

  • IBM Cloud

1. Transit Gateway Connect:

• Enables attachment of third-party SD-WAN/virtual appliances

• Provides higher bandwidth and lower latency than VPN

• Supports network transformations and advanced routing

1. Direct Connect:

• Use Transit Gateway with Direct Connect for private connectivity

• Can connect through Direct Connect partners that have presence in multiple clouds

• Provides more reliable and consistent network performance

Key Considerations:

• Need to ensure compatible routing protocols

• Must plan IP address spaces carefully to avoid overlaps

• Consider bandwidth requirements and costs

• Security groups and Network ACLs need to be properly configured

• Latency implications based on regions and connection types

Limitations:

• Cross-region routing may incur additional costs

• Some advanced features might not be available across different providers

• Need to manage different authentication mechanisms

• Bandwidth limitations vary by connection type

For production environments, it's common to use a combination of VPN and Direct Connect for redundancy and optimal performance.