NAT Instance Tutorial

What is NAT Instance?

A NAT instance provides network address translation (NAT). You can use a NAT instance to allow resources in a private subnet to communicate with destinations outside the virtual private cloud (VPC), such as the internet or an on-premises network. The resources in the private subnet can initiate outbound IPv4 traffic to the internet, but they can't receive inbound traffic initiated on the internet.

Basic Understanding

The route table associated with the private subnet sends internet traffic from the instances in the private subnet to the NAT instance in the public subnet. The NAT instance then sends the traffic to the internet gateway. The traffic is attributed to the public IP address of the NAT instance. The NAT instance specifies a high port number for the response; if a response comes back, the NAT instance sends it to an instance in the private subnet based on the port number for the response.

Step 1: Create a VPC with Public and Private Subnets

Step 2: Create Security Groups

Step 3: Launch the Public EC2 Instance

Step 4: Connect Public Instance

Step 5: Execute these CMDs

sudo yum install iptables-services -y
sudo systemctl enable iptables
sudo systemctl start iptables
echo "net.ipv4.ip_forward=1" | sudo tee /etc/sysctl.d/custom-ip.conf
sudo sysctl -p /etc/sysctl.d/custom-ip.conf
netstat -i
sudo /sbin/iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
Note: Replace 'enX0' with the correct interface (usually eth0 or ensX)
sudo /sbin/iptables -F FORWARD
sudo service iptables save

Step 6: Create an AMI from the Public EC2 (NAT)

Step 7: Launch NAT Instance from the Image

Step 8: Disable Source/Destination Check

Step 9: Launch Private EC2 Instance

Step 10: Configure Route Tables

Step 11: Connect Private EC2 Instance

Conclusion

Setting up a NAT instance in AWS is essential for resources within a private subnet to securely access the internet or on-premises networks. By configuring a NAT instance, traffic from private subnet instances is routed through a public subnet, ensuring outbound connectivity while protecting against inbound threats. This step-by-step tutorial simplifies the process, from creating VPCs and security groups to launching and testing instances. With these fundamental concepts and practical instructions, developers can effectively leverage NAT instances to enhance network connectivity and security within their AWS environments. In conclusion, a NAT instance provides a crucial bridge and this tutorial simplifies the process making it easier for developers to implement it.