You are managing a legacy application Inside VPC with hard coded IP addresses in its
configuration.
Which two mechanisms will allow the application to failover to new instances without the need for
reconfiguration?
Choose 2 answers
A.
Create an ELB to reroute traffic to a failover instance
B.
Create a secondary ENI that can be moved to a failover instance
C.
Use Route53 health checks to fail traffic over to a failover instance
D.
Assign a secondary private IP address to the primary ENIO that can De moved to a failover
instance
B and D
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bd
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Answer: B and D
This question is worded poorly, let me see if I can add an explanation. Understanding the question relies on the interpretation of “without the need for reconfiguration”. In this case, the sentence is referring to the application itself, which means manual intervention in the failover is okay and adds options B and D to the table.
Another tricky element, is where is the app is pointed with the hardcoded IP.s. I believe we can assume this to be the app itself again, b/c the app can then be distributed.
A – b/c the app is hardcoded and the ELB ip cannot be set by us (only aws), you cannot therefore, get the app to point at the ELB w/o reconfiguration so the ELB can then handle failover, removing this option from our list.
C – b/c the app is not resolving the dns names this is of no use to us as we’re not using dns resolution, which could route us to the failover if we were
That leaves B and D. From the link(http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-eni.html):
“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.”
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Ans: B & D (1.3)
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