The correct answer is that the VPCs cannot communicate because of overlapping CIDR blocks. Even though the peering connection status shows as 'active', AWS does not support VPC peering with overlapping CIDR blocks because the routing tables cannot distinguish between the two identical 10.0.0.0/16 ranges, causing traffic to be dropped or misrouted. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding that a peering connection can be established and appear active at the control plane level, but data-plane communication will fail due to ambiguous routes—a common trap where candidates assume an active status guarantees connectivity. Remember that VPC peering requires unique, non-overlapping CIDR blocks for successful routing. Memory tip: "Active status, silent failure" means the link is up but packets have no clear path.
ANS-C01 Network Implementation Practice Question
This ANS-C01 practice question tests your understanding of network implementation. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Network Topology
Refer to the exhibit. A company has two VPCs (vpc-aaaaaaaa and vpc-bbbbbbbb) that are peered. The CIDR blocks are both 10.0.0.0/16. The peering connection status is 'active'. Which of the following is true about this configuration?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The VPCs cannot communicate because of overlapping CIDR blocks
Option C is correct because overlapping CIDR blocks are not supported for VPC peering; even though the status is active, the overlapping CIDRs will cause routing issues. Option A is wrong because the peering connection can be active but routing may fail. Option B is wrong because overlapping CIDRs are not supported. Option D is wrong because DNS resolution is a separate setting.
Key principle: Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
The VPCs cannot communicate because of overlapping CIDR blocks
Why this is correct
Overlapping CIDRs prevent proper routing.
Related concept
Authentication checks who the user is.
✗
The VPC peering connection will not become active due to overlapping CIDRs
Why it's wrong here
The connection can become active but routing will not work.
✗
The VPCs can communicate using the peering connection without any issues
Why it's wrong here
Overlapping CIDRs cause routing conflicts.
✗
DNS resolution between the VPCs will be automatically enabled
Why it's wrong here
DNS resolution must be explicitly enabled and does not fix overlapping CIDRs.
Common exam traps
Common exam trap: authentication is not authorization
Logging in proves the user can authenticate. It does not automatically mean the user is allowed to enter privileged or configuration mode. Watch for AAA authorization, privilege level and command authorization details.
Detailed technical explanation
How to think about this question
This kind of question is testing the difference between identity and permission. A user may successfully log in to a router because authentication is working, but still fail to enter configuration mode because authorization is missing, misconfigured or mapped to a lower privilege level.
KKey Concepts to Remember
Authentication checks who the user is.
Authorization controls what the user is allowed to do after login.
Privilege levels affect access to EXEC and configuration commands.
AAA, TACACS+ and RADIUS can separate login success from command access.
TExam Day Tips
→Do not assume successful login means full administrative access.
→Look for words such as cannot enter configuration mode, privilege level, authorization or command access.
→Separate login problems from permission problems before choosing the answer.
Key takeaway
Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Real-world example
How this comes up in practice
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
Got this wrong? Here's your next step.
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related ANS-C01 questions on access control and AAA configuration.
Network Implementation — This question tests Network Implementation — Authentication checks who the user is..
What is the correct answer to this question?
The correct answer is: The VPCs cannot communicate because of overlapping CIDR blocks — Option C is correct because overlapping CIDR blocks are not supported for VPC peering; even though the status is active, the overlapping CIDRs will cause routing issues. Option A is wrong because the peering connection can be active but routing may fail. Option B is wrong because overlapping CIDRs are not supported. Option D is wrong because DNS resolution is a separate setting.
What should I do if I get this ANS-C01 question wrong?
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related ANS-C01 questions on access control and AAA configuration.
What is the key concept behind this question?
Authentication checks who the user is.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.