AWS VPC Peering Using Terraform: A Comprehensive Guide

By /

Listen to this Post

Featured Image
Virtual Private Clouds (VPCs) in AWS provide isolated network environments, but sometimes resources in different VPCs need to communicate. VPC peering enables secure, direct connectivity between VPCs, whether they reside in the same or different AWS accounts.

You Should Know:

1. Prerequisites for VPC Peering

  • Non-overlapping CIDR blocks for the VPCs.
  • Proper route table configurations.
  • Security groups and NACLs allowing necessary traffic.

2. Terraform Code for VPC Peering

Below is a verified Terraform script to establish VPC peering:

 Define VPCs
resource "aws_vpc" "vpc1" {
cidr_block = "10.0.0.0/16"
}

resource "aws_vpc" "vpc2" {
cidr_block = "192.168.0.0/16"
}

Create VPC Peering Connection
resource "aws_vpc_peering_connection" "peer" {
peer_vpc_id = aws_vpc.vpc2.id
vpc_id = aws_vpc.vpc1.id
auto_accept = true  Only works if same AWS account
}

Update Route Tables
resource "aws_route_table" "rt1" {
vpc_id = aws_vpc.vpc1.id

route {
cidr_block = aws_vpc.vpc2.cidr_block
gateway_id = aws_vpc_peering_connection.peer.id
}
}

resource "aws_route_table" "rt2" {
vpc_id = aws_vpc.vpc2.id

route {
cidr_block = aws_vpc.vpc1.cidr_block
gateway_id = aws_vpc_peering_connection.peer.id
}
}

3. Key AWS CLI Commands

Verify VPC peering status:

aws ec2 describe-vpc-peering-connections --query "VpcPeeringConnections[?Status.Code == 'active']"

Check route table updates:

aws ec2 describe-route-tables --route-table-ids <RT_ID>

4. Troubleshooting Steps

  • Ensure auto-accept is enabled for same-account peering.
  • For cross-account peering, manually accept the request: 
    aws ec2 accept-vpc-peering-connection --vpc-peering-connection-id <PEER_ID>
  • Verify Security Group rules allow traffic between peered VPCs.

5. Alternative: AWS Transit Gateway

For multiple VPCs, consider Transit Gateway:

resource "aws_ec2_transit_gateway" "tgw" {
description = "Centralized VPC connectivity"
}

resource "aws_ec2_transit_gateway_vpc_attachment" "attach1" {
subnet_ids = [aws_subnet.vpc1_subnet.id]
transit_gateway_id = aws_ec2_transit_gateway.tgw.id
vpc_id = aws_vpc.vpc1.id
}

What Undercode Say:

AWS VPC peering is a powerful feature for secure inter-VPC communication. However, managing multiple peerings can become complex—Transit Gateway simplifies this for large-scale architectures.

Expected Output:

  • Successful peering connection (active status).
  • Updated route tables directing traffic via the peering connection.
  • Verified connectivity (e.g., via `ping` or `telnet` tests).

For further reading:

Prediction:

As hybrid cloud adoption grows, demand for automated VPC networking (Terraform/CloudFormation) will rise, with Transit Gateway becoming the standard for multi-VPC architectures.

References:

Reported By: Darryl Ruggles – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

Join Our Cyber World:

💬 Whatsapp | 💬 Telegram

Related Posts: