Crucial Exams

AWS Certified CloudOps Engineer Associate SOA-C03 Practice Question

After migrating a three-tier web application to a VPC, web servers in a public subnet cannot open MySQL connections to an Amazon RDS instance in a private subnet. All related security groups already allow TCP port 3306. The engineer enables VPC flow logs on the database subnet and sees multiple entries similar to:

10.0.10.15 10.0.20.42 3306 44321 6 64 40 1680567227 1680567287 REJECT OK

Which VPC layer is most likely dropping the traffic, and what should the engineer investigate first?

  • Source/destination check is still enabled on the web server ENIs; disable it so return traffic is forwarded correctly.

  • The route table for the database subnet lacks a local target; add a route that points 10.0.0.0/16 to the local gateway.

  • A stateless network ACL associated with the RDS subnet is denying the connection; inspect and update its inbound and outbound rules.

  • The RDS instance's security group is rejecting the SYN packet; verify and correct its outbound rules.

AWS Certified CloudOps Engineer Associate SOA-C03
Networking and Content Delivery
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