Question about correct answer for question number 3 in SAA-C03 exam sample question on aws page:
https://aws.amazon.com/certification/certified-solutions-architect-associate/
PDF with sample questions:
https://d1.awsstatic.com/training-and-certification/docs-sa-assoc/AWS-Certified-Solutions-Architect-Associate_Sample-Questions.pdf
In my opinion answer A is correct and C answer is incorrect.
Because it is not possible to have the same private IP address assigned to two Elastic Network Interfaces (ENIs) in AWS. Each network interface must have a unique IP address assigned to it within the subnet it is associated with.
Whole question and answer options:
A company plans to run a monitoring application on an Amazon EC2 instance in a VPC. Connections are made to the EC2 instance using the instance’s private IPv4 address. A solutions architect needs to design a solution that will allow traffic to be quickly directed to a standby EC2 instance if the application fails and becomes unreachable. Which approach will meet these requirements?
A) Deploy an Application Load Balancer configured with a listener for the private IP address and register the primary EC2 instance with the load balancer. Upon failure, de-register the instance and register the standby EC2 instance.
B) Configure a custom DHCP option set. Configure DHCP to assign the same private IP address to the standby EC2 instance when the primary EC2 instance fails.
C) Attach a secondary elastic network interface to the EC2 instance configured with the private IP address. Move the network interface to the standby EC2 instance if the primary EC2 instance becomes unreachable.
D) Associate an Elastic IP address with the network interface of the primary EC2 instance. Disassociate the Elastic IP from the primary instance upon failure and associate it with a standby EC2 instance.
AWS OFFICIALUpdated 2 years ago
Ok, in this case C anwer will work, if traffic from begining will directed to sesond ENI, and IF we have some possibility to quick attach and detach ENI between EC2 instances. My mistaken thinking was based on premise that trafffic directed to primary ENI's IP... and that we have dns for private IP's
And A answer is incorrect because ALB working only with DNS names? In real life is ALB using is more sensible then ping-pong ENI? Or this solution is aws specific?
I think the scenario is very specific to see if you know secondary ENIs can be attached and detached. The subnets are defined when you create the ALB, not when you create the listener. Plus ALBs only handle HTTP and HTTPS protocols.
Thank you for your responses!