How to Retrieve the IP Address of an EC2 Instance in an Autoscaling Group

Answer - A.

This is given in the AWS Documentation.

Instance metadata is data about your instance that you can use to configure or manage the running instance.

Because your instance metadata is available from your running instance, you do not need to use the Amazon EC2 console or the AWS CLI.

This can be helpful when you're writing scripts to run from your instance.

For example, you can access the local IP address of your instance from instance metadata to manage a connection to an external application.

Since the data can only be retrieved from the Instance Metadata, all other options are invalid.

For more information on Instance Metadata, please refer to the below URL-

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-metadata.html

The correct answer is A. Make the application query the Instance Metadata.

When an EC2 instance launches, it automatically receives metadata that can be accessed using a well-known URL. EC2 instance metadata is a simple way to get information about an instance, such as the instance ID, public IP address, private IP address, and more.

To get the IP address of the EC2 instance, the application can make a query to the instance metadata URL: http://169.254.169.254/latest/meta-data/local-ipv4.

This URL will return the private IP address of the instance. If the instance has a public IP address, you can use http://169.254.169.254/latest/meta-data/public-ipv4 to get it.

Option B, making the application query the Instance Userdata, is not the correct answer because user data is a piece of information that can be passed to the EC2 instance when it launches. It is typically used to run scripts or set up the instance's environment. It does not contain information about the instance itself.

Option C, making the application query the Autoscaling Group, is also not the correct answer. The Autoscaling Group is a logical grouping of EC2 instances that can be automatically scaled up or down based on demand. While it does contain information about the instances in the group, it does not provide their IP addresses.

Option D, making the application query the Launch configuration, is also not the correct answer. The Launch configuration is a template that is used to launch EC2 instances in an Autoscaling Group. It contains information such as the AMI ID, instance type, security groups, and other launch parameters. It does not contain information about the IP addresses of the instances that are launched.