How to do it...

1. I have created one more EC2 instance as visible in the Instances section of the EC2 console.

1. Click on Elastic IPs in the left menu bar.

1. Click on Allocate new address.

1. Click on Allocate.

1. Click on Close. The Elastic IP page will be visible. Choose Elastic IP and click on Actions | Associate address.

1. Choose Instance in the Resource type. Select Nat Instance from the Instance drop-down menu. Click on Associate. A success message is shown.

1. Go to the Instances menu. You can see that the public DNS and IPv4 public IP has changed. You can see Change Source/Dest. Check is true for the instance.

1. Select Actions | Networking | Change Source/Dest. Check.

1. You can see that Change Source/Dest. Check is now false.

1. We need to update the main Route Table attached to the VPC. Let's go back to the VPC dashboard and select our VPC.

1. Click on the Route Tables starting with rtb.

1. Select the Route Table and navigate to the Routes tab. Click on the Edit button. Add 0.0.0.0/0 in the destination and the NAT instance ID in Target. Click Save.