What is VPC Peering in AWS?

VPC Peering is a networking connection between two Amazon VPCs (Virtual Private Clouds) that allows them to communicate privately as if they were in the same network.

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🔹 Why Use VPC Peering?

• Private Communication: Resources in different VPCs can talk to each other without using the internet.

• High Performance & Low Latency: It runs on the AWS backbone network, making it fast and secure.

• Cross-Account & Cross-Region Support: You can link up VPCs in different AWS accounts and even in different regions (thanks to inter-region peering).

• No Single Point of Failure: It's a direct connection between VPCs, so you don't have to rely on a third-party service.

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🔹 How VPC Peering Works?

1. Request Peering: The owner of VPC A sends a peering request to the owner of VPC B.

2. Accept Peering: The owner of VPC B accepts the request.

3. Update Route Tables: Both VPCs must update their route tables to allow traffic to flow between them.

4. Communication Enabled: Resources (EC2, RDS, etc.) in both VPCs can now communicate.

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🔹 Example: VPC Peering Setup

Imagine you have two VPCs:

• VPC A (10.0.0.0/16) - N.Virginia

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• VPC B (192.168.0.0/16) - OHIO

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To enable communication:

1. Create a VPC Peering connection.

   

2. Accept the peering request.

3. Update VPC A’s route table to point traffic for 192.168.0.0/16 to VPC B.

   

4. Update VPC B’s route table to point traffic for 10.0.0.0/16 to VPC A.

   

   5. Now try to ping each other (server ) on to their private ip.

      

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🔹 Key Limitations of VPC Peering

1. No Transitive Peering: If VPC A is peered with VPC B, and VPC B is peered with VPC C, then VPC A & C cannot communicate. You’d need a direct peering connection.

2. No Overlapping CIDRs: The CIDR blocks of the VPCs must be unique (cannot overlap).

3. Manual Route Updates: You must manually update route tables in both VPCs.

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🔹 Alternative to VPC Peering

✅ AWS Transit Gateway – A better option for managing multiple VPCs at scale, allowing centralized routing instead of multiple peering connections.

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