ANS-C01 VPC Peering Practice Question
A network engineer is troubleshooting connectivity between two VPCs connected via a VPC peering connection. Security groups and NACLs are configured correctly. The engineer verifies that the route tables have the necessary entries. However, traffic from an EC2 instance in VPC A to an RDS instance in VPC B fails. Which TWO additional checks should be performed? (Choose two.)
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Check that the security group attached to the RDS instance allows inbound traffic from the CIDR block of VPC A.
The correct checks to perform when troubleshooting VPC peering connectivity are to ensure the VPC peering connection is in the 'active' state (Option E) and that the security group attached to the RDS instance allows inbound traffic from the CIDR block of VPC A (Option A). Without an active peer connection, traffic cannot flow even if route tables are correct. Similarly, security group rules are stateful and must explicitly permit inbound traffic; NACLs are stateless but since the issue is within the same VPC peering, security groups are a likely culprit. IAM roles and Internet Gateways are not required for VPC peering traffic.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Check that the security group attached to the RDS instance allows inbound traffic from the CIDR block of VPC A.
Why this is correct
Correct: Security groups must allow traffic from peer VPC.
- ✗
Verify that the network ACLs in both VPCs have appropriate inbound and outbound rules for the traffic.
Why it's wrong here
Wrong: NACLs are already verified correct.
- ✗
Confirm that the VPCs have an Internet Gateway attached.
Why it's wrong here
Wrong: Internet Gateway is not required for VPC peering.
- ✗
Check that the EC2 instance has an IAM role that allows it to communicate with RDS.
Why it's wrong here
Wrong: IAM roles are not needed for network connectivity.
- ✓
Ensure that the VPC peering connection is in the 'active' state.
Why this is correct
Correct: Peering must be active for traffic to flow.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This ANS-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the ANS-C01 exam.