vpc peering and tgw diff

VPC Peering

VPC Peering is a networking connection between two VPCs that enables you to route traffic between them privately. Think of it as a direct highway between two cities.

Transit Gateway

AWS Transit Gateway acts as a cloud router — a hub that controls how traffic is directed between VPCs and on-premises networks. Imagine it as a central train station where multiple rail lines (VPCs) converge.

Key Differences

1

Scalability

VPC Peering:

• Requires individual connections between each pair of VPCs

• Following the formula n(n-1)/2, connecting 10 VPCs requires 45 peering connections

• Becomes complex to manage at scale

Transit Gateway:

• Hub-and-spoke model

• Each VPC only needs one connection to the Transit Gateway

• 10 VPCs only require 10 connections

2

Cost Considerations

VPC Peering:

• No additional charge for the peering connection itself

• Pay only for data transfer between VPCs

• More cost-effective for simple architectures with few VPCs

Transit Gateway:

• Hourly charges for each attachment and data processing

• Higher cost but simplified management

• Cost increases with the number of attachments and data transfer

3

Routing Capabilities

VPC Peering:

• Only supports direct VPC-to-VPC communication

• Transitive routing is not supported

• Each connection needs separate route table entries

Transit Gateway:

• Supports transitive routing between all attached networks

• Can implement complex routing policies

• Centralized route management

• Supports route tables and routing domains

When to Choose What?

1

Choose VPC Peering When:

• You have a simple network topology (2–3 VPCs)

• Direct communication between specific VPCs is needed

• Cost optimization is a primary concern

• You don’t need advanced routing features

• You’re operating within a single region

2

Choose Transit Gateway When:

• You have a complex network topology (4+ VPCs)

• You need centralized network management

• You require transitive routing

• You need to connect to on-premises networks

• You’re implementing a hub-and-spoke network architecture

• You need cross-region connectivity

Real-World Example

Let’s consider a typical enterprise scenario:

• Production VPC

• Development VPC

• Shared Services VPC

• Data Analytics VPC

• On-premises network via Direct Connect

VPC Peering Approach:

• Would require 10 peering connections to achieve full connectivity:

  • Prod ↔ Dev

  • Prod ↔ Shared Services

  • Prod ↔ Data Analytics

  • Dev ↔ Shared Services

  • Dev ↔ Data Analytics

  • Shared Services ↔ Data Analytics

• Plus additional complexity for on-premises connectivity

Transit Gateway Approach:

• Single connection from each VPC to Transit Gateway

• One Direct Connect connection to Transit Gateway

• Centralized routing control

• Easier to add new VPCs

Best Practices

1

Document Your Requirements

• Number of VPCs

• Expected traffic patterns

• Growth projections

• Security requirements

2

Consider Future Growth

• Will you add more VPCs?

• Are there plans for multi-region expansion?

• Potential for mergers or acquisitions?

3

Evaluate Total Cost of Ownership

• Include management overhead

• Consider operational costs

• Factor in training requirements

Conclusion

While VPC Peering is perfect for simple, cost-effective connections between a few VPCs, Transit Gateway shines in complex environments where centralized management and scalability are crucial. The choice between them should be based on your specific requirements, future growth plans, and operational capabilities.

Remember: Network architecture decisions have long-lasting implications. Take time to evaluate your needs thoroughly before making a choice.