What IP address is used to retrieve instance metadata of userdata in AWS?

The correct choice is based on the fact that AWS instances can access their metadata and user data through a special link-local IP address, specifically 169.254.169.254. This address is reserved for instance metadata services and allows instances to retrieve various details about themselves, including instance IDs, security groups, and user data.

When an instance makes an HTTP request to this address, it can access important information crucial for applications running on that instance. User data, which is often used for configuration scripts or initialization tasks during the instance boot process, can be fetched from this metadata endpoint.

The other options represent either general public IP addresses or localhost, which are not designed for accessing instance metadata. Public IP addresses would typically not route to a specific instance's metadata, and using localhost would refer to the loopback interface of the instance, which cannot provide metadata information. Hence, the designated address of 169.254.169.254 is the only appropriate choice for retrieving instance metadata, emphasizing its critical role in AWS architecture for instance configuration and management.