ANS-C01 Network Security, Compliance and Governance Practice Question
A company has a VPC peered with another VPC in a different account. They want to ensure that only specific ports are allowed from the peered VPC to their application servers. Which configuration should they use?
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
✓
Configure a Security Group rule with the security group ID of the peered VPC
You can reference a security group from a peered VPC as the source in a security group rule, allowing fine-grained control based on the security group ID rather than CIDR blocks. Option A is wrong because VPC peering route tables control routing, not traffic filtering. Option B is wrong because security groups can reference the CIDR of a peered VPC, but that does not allow specifying individual ports from the peered VPC's resources; it's less specific than referencing the security group ID. Option D is wrong because Network ACLs cannot reference security groups; they only allow CIDR-based rules, and they are stateless.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use a VPC peering route table to restrict traffic
Why it's wrong here
Route tables do not filter traffic; they only route.
- ✗
Configure a Security Group rule with the CIDR of the peered VPC
Why it's wrong here
Security Groups can reference CIDR, but best practice is to reference the security group of the peered VPC for dynamic updates.
- ✓
Configure a Security Group rule with the security group ID of the peered VPC
Why this is correct
Security Groups can reference security groups in peered VPCs for fine-grained access.
- ✗
Configure a Network ACL rule with the CIDR of the peered VPC
Why it's wrong here
A Network ACL is stateless, so it cannot track connection state; it would require separate inbound and outbound rules for return traffic, which the scenario’s requirement for port-specific control from a peered VPC does not address. This option tempts because Network ACLs do filter traffic by CIDR and port at the subnet boundary, and would be correct for stateless, subnet-level access control where the application servers do not initiate responses.
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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.