What is one action a developer needs to take after adding a NAT instance to ensure proper internet access for private subnet instances?

To ensure that instances in a private subnet have proper internet access through a NAT instance, configuring a route table is essential. A route table directs traffic within a VPC and determines where network traffic from your subnets is directed.

When instances in the private subnet need to communicate with the internet, they cannot do so directly since they do not have a public IP address. Instead, traffic from these instances must be routed to the NAT instance, which has a public IP. By configuring the route table associated with the private subnet, you can specify that any outbound internet traffic should be directed to the NAT instance's private IP address. This configuration enables the NAT instance to forward requests to the internet and relay the responses back to the private instances.

Other options, such as assigning a public IP to the NAT or propagating the instance's Elastic IP, do not address the fundamental need for routing. Disabling security groups is also not a recommended approach, as security groups are essential for managing access to AWS resources and should normally remain enabled to maintain proper security measures. By focusing on the route table setup, the private subnet instances can successfully send and receive traffic through the NAT instance to and from the internet.