A small company started using EBS backed EC2 instances for the cost improvements over their own running servers. The company’s policy is to stop the development servers over the weekend and restart them next week. The first time when the servers were brought back, none of the developers were able to SSH into them. What did the server most likely overlook?

Answer options:

A.The associated Elastic IP address has changed and the SSH configurations were not updated.
B.The security group for a stopped instance needs to be reassigned after the start.
C.The public IPv4 address has changed on the server start and the SSH configurations were not updated.
D.EBS backed EC2 instances could not be stopped and were automatically terminated.

Correct Answer: C
Option C is correct. The instance retains its private IPv4 addresses and any IPv6 addresses when stopped and started. AWS releases public IPv4 address and assigns a new one when it is stopped & started.
Option A is incorrect. An EC2 instance retains its associated Elastic IP addresses.
Option B is incorrect. Security groups do not need to be reassigned to instances that are restarted.
Option D is incorrect. EBS backed instances are the only instance type that can be started and stopped.
Reference:
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/Stop_Start.html