You’ve currently configured health checks in Route 53. These health checks are being used for 2 of your on-premises web servers. The health checks are not working as desired. The health checks are continually failing. Which of the following could be a possible reason?

Answer options:

A.Ensure that the Security groups on the Instances are allowing Inbound Traffic.
B.Ensure that the NACLs on the Subnets are allowing Inbound Traffic.
C.Ensure that the Firewall on your On-premises environment is allowing Inbound Traffic.
D.This is not possible. You cannot enable health checks for non-AWS resources.

Answer – C
The AWS Documentation mentions the following.
When Route 53 checks the health of an endpoint, it sends an HTTP, HTTPS, or TCP request to the IP address and port that you specified when you created the health check. For a health check to succeed, your router and firewall rules must allow inbound traffic from the IP addresses that the Route 53 health checkers use.
Options A and B are invalid because the health checks are not being configured for EC2 Instances.
Option D is incorrect because it is possible to use AWS Route 53 for monitoring non-AWS resources.
For more information on Route 53 health checks, please refer to the below URL
https://docs.aws.amazon.com/Route53/latest/DeveloperGuide/dns-failover-router-firewall-rules.html