AWScloud~5 mins

Route tables configuration in AWS - Commands & Configuration

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Introduction

Route tables control where network traffic goes inside your cloud network. They help your servers and devices talk to each other and to the internet safely and correctly.

When you want to connect your cloud servers to the internet through a gateway.

When you need to allow communication between different parts of your cloud network.

When you want to block or allow traffic to specific destinations.

When setting up private networks that need to access public services securely.

When you want to control traffic flow for security or performance reasons.

Config File - main.tf

main.tf

provider "aws" {
  region = "us-east-1"
}

resource "aws_vpc" "example_vpc" {
  cidr_block = "10.0.0.0/16"
  tags = {
    Name = "example-vpc"
  }
}

resource "aws_internet_gateway" "example_igw" {
  vpc_id = aws_vpc.example_vpc.id
  tags = {
    Name = "example-igw"
  }
}

resource "aws_route_table" "example_route_table" {
  vpc_id = aws_vpc.example_vpc.id
  tags = {
    Name = "example-route-table"
  }
}

resource "aws_route" "internet_access" {
  route_table_id         = aws_route_table.example_route_table.id
  destination_cidr_block = "0.0.0.0/0"
  gateway_id             = aws_internet_gateway.example_igw.id
}

resource "aws_subnet" "example_subnet" {
  vpc_id            = aws_vpc.example_vpc.id
  cidr_block        = "10.0.1.0/24"
  availability_zone = "us-east-1a"
  tags = {
    Name = "example-subnet"
  }
}

resource "aws_route_table_association" "example_association" {
  subnet_id      = aws_subnet.example_subnet.id
  route_table_id = aws_route_table.example_route_table.id
}

This Terraform file creates a virtual private cloud (VPC) with a subnet and an internet gateway. It defines a route table that sends all traffic (0.0.0.0/0) to the internet gateway, allowing internet access. The route table is then linked to the subnet so that instances in the subnet use this route.

provider: sets the AWS region.

aws_vpc: creates a private network.

aws_internet_gateway: allows internet access.

aws_route_table: holds routing rules.

aws_route: defines a rule sending all traffic to the internet gateway.

aws_subnet: a smaller network inside the VPC.

aws_route_table_association: links the route table to the subnet.

Commands

This command prepares Terraform to work with AWS by downloading necessary plugins and setting up the environment.

Terminal

terraform init

Expected OutputExpected

Initializing the backend... Initializing provider plugins... - Finding latest version of hashicorp/aws... - Installing hashicorp/aws v4.60.0... - Installed hashicorp/aws v4.60.0 (signed by HashiCorp) Terraform has been successfully initialized!

This command creates the VPC, subnet, internet gateway, route table, and associations as defined in the configuration file.

Terminal

terraform apply -auto-approve

Expected OutputExpected

aws_vpc.example_vpc: Creating... aws_vpc.example_vpc: Creation complete after 3s [id=vpc-0a1b2c3d4e5f6g7h8] aws_internet_gateway.example_igw: Creating... aws_internet_gateway.example_igw: Creation complete after 2s [id=igw-0a1b2c3d4e5f6g7h8] aws_route_table.example_route_table: Creating... aws_route_table.example_route_table: Creation complete after 2s [id=rtb-0a1b2c3d4e5f6g7h8] aws_route.internet_access: Creating... aws_route.internet_access: Creation complete after 1s aws_subnet.example_subnet: Creating... aws_subnet.example_subnet: Creation complete after 3s [id=subnet-0a1b2c3d4e5f6g7h8] aws_route_table_association.example_association: Creating... aws_route_table_association.example_association: Creation complete after 1s [id=rtbassoc-0a1b2c3d4e5f6g7h8] Apply complete! Resources: 6 added, 0 changed, 0 destroyed.

→

-auto-approve - Automatically approves the plan without asking for confirmation

This command checks the route tables in the VPC to verify the routes are set correctly.

Terminal

aws ec2 describe-route-tables --filters "Name=vpc-id,Values=vpc-0a1b2c3d4e5f6g7h8"

Expected OutputExpected

{ "RouteTables": [ { "RouteTableId": "rtb-0a1b2c3d4e5f6g7h8", "Routes": [ { "DestinationCidrBlock": "0.0.0.0/0", "GatewayId": "igw-0a1b2c3d4e5f6g7h8", "State": "active", "Origin": "CreateRoute" } ] } ] }

→

--filters - Filters results to show only route tables for the specified VPC

Key Concept

If you remember nothing else from this pattern, remember: route tables tell your cloud network where to send traffic, like a map for your data.

Common Mistakes

Not associating the route table with the subnet

Without association, the subnet won't use the route table rules, so traffic won't flow as expected.

Always create a route table association resource linking your route table to the subnet.

Setting the destination CIDR block incorrectly, like using 0.0.0.0/1 instead of 0.0.0.0/0

Traffic won't route properly if the destination range is wrong, causing connectivity issues.

Use 0.0.0.0/0 to represent all IPv4 addresses for internet-bound traffic.

Forgetting to create or attach an internet gateway when routing to the internet

Without an internet gateway, traffic cannot leave the VPC to reach the internet.

Create an internet gateway and reference its ID in the route table for internet traffic.

Summary

Initialize Terraform to prepare AWS provider plugins.

Apply the Terraform configuration to create VPC, subnet, internet gateway, route table, and associations.

Verify the route table has the correct route sending all traffic to the internet gateway.

Practice

(1/5)

1. What is the main purpose of a route table in AWS networking?

easy

A. To manage user permissions

B. To store user data securely

C. To direct network traffic between subnets and gateways

D. To monitor server health

Route tables configuration in AWS - Commands & Configuration

Start learning this pattern below

Practice

Solution

Step 1: Understand the role of route tables

Step 2: Identify what route tables connect

Final Answer:

Quick Check:

Solution

Step 1: Identify the correct AWS CLI command for association

Step 2: Check the correct syntax and parameters

Final Answer:

Quick Check:

Solution

Step 1: Analyze the route for 0.0.0.0/0

Step 2: Determine route for 8.8.8.8

Final Answer:

Quick Check:

Solution

Step 1: Check route table routes for internet access

Step 2: Identify missing or incorrect routes

Final Answer:

Quick Check:

Solution

Step 1: Understand NAT gateway purpose

Step 2: Configure Subnet B's route table (NAT subnet)

Step 3: Configure Subnet A's route table

Final Answer:

Quick Check: