Exam AWS Certified Solutions Architect - Professional topic 1 question 353 discussion

To ensure failover capabilities on an elastic network interface (ENI), you should use a secondary private IP for incoming traffic. When you attach an elastic network interface (ENI) to an Amazon EC2 instance, it can have one or more private IP addresses associated with it. By assigning a secondary private IP address to the ENI, you can configure failover capabilities. To achieve failover, you can associate the secondary private IP address with a separate network interface on a standby instance. This standby instance can be in the same or a different availability zone. If the primary instance or ENI fails, you can quickly reassign the secondary private IP address to the standby instance, redirecting incoming traffic to the backup instance. Therefore, the correct answer is B. A secondary private IP.

ok, it is B, but this question is terribly written. It is in regards of floating ip involving active/standby instances

B. "ensure failover capabilities, consider using a secondary private IPv4" https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/scenarios-enis.html

Correct Answer is B https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/scenarios-enis.html

For me it's letter D - Secondary ENI. When we move the secondary ENI from one failed instance to a standby instance the ENI goes with its primary private IP, secondary IP, public IP, MAC, etc... https://docs.amazonaws.cn/en_us/AWSEC2/latest/UserGuide/scenarios-enis.html

B. A secondary private IP

To ensure failover capabilities, consider using a secondary private IPv4 for incoming traffic on a network interface. In the event of an instance failure, you can move the interface and/or secondary private IPv4 address to a standby instance. https://docs.amazonaws.cn/en_us/AWSEC2/latest/UserGuide/scenarios-enis.html

plus the question states "for incoming traffic"

For me should be answer A : a Route53 A Record. You have an ENI you do not know if the failover must cover a front end (public IP) or back end (private IP) instance to reattach the ENI to. An ENI by itself is not sufficient without any action or script, neither is a secondary ENI. Therefore an A record with the IP of this ENI would be a sufficient configuration to failover to it

B https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-eni.html

Why is D wrong?

Cant disconnect a primary ENI

I don't get this. ENI maintains Primary Private IPv4. Why need Secondary Private IPv4 for incoming traffic? Just detach and attach to Standby instance and have the incoming traffic use Primary.