Your company is hosting an application on an EC2 Instance. The application is a high revenue-generating application. Hence it needs to be ensured that it can be easily shifted to another EC2 Instance if the primary one goes down. You have created an AMI so that it can be used to spin up a secondary instance. Which of the following can also help ensure a smooth switchover of the application onto a new instance if the primary one fails?

Answer options:

A.Assign a secondary ENI to the primary instance.
B.Assign an Elastic IP to the primary instance.
C.Create a secondary Internet gateway for the VPC.D.Create a secondary NAT gateway for the VPC.

Correct Answer: B
The AWS Documentation mentions the following.
You can disassociate an Elastic IP address from a resource, and reassociate it with a different resource. Any open connections to an instance continue to work for a time even after you disassociate its Elastic IP address and reassociate it with another instance. We recommend that you reopen these connections using the reassociated Elastic IP address.
Option A is incorrect since the ENI would not help since the IP addressing is different for secondary ENI’s.
Option C is incorrect since the Internet gateway is already a durable and highly available software.
Option D is incorrect since there is no mention of traffic needing to pass through the Internet from a private subnet.
For more information on Elastic IP addressing, please refer to the below URL-
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/elastic-ip-addresses-eip.html