Скачать или смотреть Resolving Access Issues in Your AWS VPC: Connecting Private Subnets and Internet Egress

Learn how to set up your AWS VPC to allow resources in a private subnet to communicate with each other and access the internet seamlessly.
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This video is based on the question https://stackoverflow.com/q/68156872/ asked by the user 'diegoaguilar' ( https://stackoverflow.com/u/742560/ ) and on the answer https://stackoverflow.com/a/68157005/ provided by the user 'Marcin' ( https://stackoverflow.com/u/248823/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Introduction

When managing resources in an Amazon Web Services (AWS) Virtual Private Cloud (VPC), problems can arise when you try to connect services on a private subnet to the internet. This can lead to complications, especially when dealing with services like CodeBuild, Elastic Cache, and others. Recently, a user faced challenges connecting their resources, resulting in timeouts while trying to access S3 for build purposes. This guide will help you navigate through these issues and implement the right configurations.

Identifying the Problem

The user had a setup involving:

One VPC

One private subnet

One NAT gateway

Security group with egress and ingress rules

Despite this configuration, the CodeBuild instance was unable to connect to S3, which led to a timeout error. The primary issues identified were:

Misconfiguration of the network components

Placement of the NAT gateway

Lack of proper routing for public subnets

Solution Overview

To resolve the connectivity issues, we need to implement the following changes:

Create a Public Subnet: A public subnet allows your resources to communicate with the internet.

Internet Gateway: This component is essential for enabling internet access for public subnets.

Correct Placement of the NAT Gateway: The NAT gateway should reside within the public subnet, not in the private subnet.

Proper Route Tables: Ensure that public and private subnets have appropriate routing rules.

Step-by-Step Configuration

1. Define Your VPC and Subnets

You need to create the VPC and the necessary subnets for both private and public access. Use the following configurations:

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2. Create an Internet Gateway

An internet gateway is critical for allowing public access. Add this resource to your configuration:

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3. Setup NAT Gateway

Configure the NAT Gateway to be positioned in the public subnet, ensuring that private resources can access the internet:

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4. Configure Route Tables

Ensure that your public and private subnets are associated with their respective route tables:

The public route table should direct all outbound traffic through the internet gateway.

The private route table should route outbound traffic through the NAT gateway.

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5. Security Groups and Network ACL Configuration

Although it's not covered in detail here, ensure that your Security Groups (SGs) allow the necessary traffic (like Redis traffic on port 6379) and that your Network ACLs do not block the required traffic.

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Conclusion

Implementing a VPC with the correct configurations is crucial for ensuring that resources can communicate with each other and access external services. By following the outlined steps above, including creating an internet gateway and placing your NAT gateway correctly, you will enable connectivity from your private subnet to the internet, fixing the issues that inhibited your CodeBuild from accessing S3.

With your new understanding, go forth and optimize your AWS environment!