ANS-C01 Network Management and Operations Practice Question
This ANS-C01 practice question tests your understanding of network management and operations. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
A network engineer is troubleshooting connectivity between two VPCs that are peered. The VPC peering connection is active, and the route tables have appropriate routes. However, instances in VPC A cannot reach instances in VPC B. The security groups in both VPCs allow all traffic. What is the most likely issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The route tables in both VPCs do not have routes pointing to the peering connection for the other VPC's CIDR
VPC peering does not support transitive routing; if there is an intermediate resource (like a VPN or another VPC) involved, it won't work. But the question doesn't mention that. Another common issue is that the VPC peering connection requires that the route tables of both VPCs have routes to each other's CIDR, and that security groups reference each other's CIDR or security group IDs. Since security groups allow all, the issue might be that the security group rules are not allowing traffic from the peer VPC's CIDR. However, since they allow all, the problem is likely that the instances are in different regions and the peering is intra-region? Actually, VPC peering works across regions but requires appropriate route table entries. The most likely issue is that the route tables are missing the necessary routes. Option A is correct.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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 security groups are not allowing ICMP traffic
Why it's wrong here
Security groups allow all traffic per the problem.
✓
The route tables in both VPCs do not have routes pointing to the peering connection for the other VPC's CIDR
Why this is correct
Without these routes, traffic cannot traverse the peering connection.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
The VPC peering connection is not in the 'active' state
Why it's wrong here
The problem states it is active.
✗
The instances are in different availability zones
Why it's wrong here
Availability zones do not affect VPC peering connectivity.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
Network Management and Operations — This question tests Network Management and Operations — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The route tables in both VPCs do not have routes pointing to the peering connection for the other VPC's CIDR — VPC peering does not support transitive routing; if there is an intermediate resource (like a VPN or another VPC) involved, it won't work. But the question doesn't mention that. Another common issue is that the VPC peering connection requires that the route tables of both VPCs have routes to each other's CIDR, and that security groups reference each other's CIDR or security group IDs. Since security groups allow all, the issue might be that the security group rules are not allowing traffic from the peer VPC's CIDR. However, since they allow all, the problem is likely that the instances are in different regions and the peering is intra-region? Actually, VPC peering works across regions but requires appropriate route table entries. The most likely issue is that the route tables are missing the necessary routes. Option A is correct.
What should I do if I get this ANS-C01 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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