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 intermittent connectivity issues between two VPCs connected via a VPC peering connection. The engineer notices that the route tables in both VPCs have the correct routes. What should the engineer check next?
Check security group and network ACL rules
Security groups and NACLs can block traffic even with correct routes.
Verify that DNS resolution is enabled for the VPCs
Why wrong: DNS resolution does not affect basic IP connectivity.
Ensure that the VPN connection is active
Why wrong: VPN connection is not relevant to VPC peering.
Check the internet gateway configuration
Why wrong: Internet gateway is not used in VPC peering.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Check security group and network ACL rules
Option A is correct because security group rules and NACLs can block traffic even if routes are correct. Option B is wrong because DNS resolution is not related to basic connectivity. Option C is wrong because internet gateway is not involved in VPC peering. Option D is wrong because VPN connection is a different service.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Check security group and network ACL rules
Why this is correct
Security groups and NACLs can block traffic even with correct routes.
Related concept
Standard ACLs match source addresses.
Verify that DNS resolution is enabled for the VPCs
Why it's wrong here
DNS resolution does not affect basic IP connectivity.
Ensure that the VPN connection is active
Why it's wrong here
VPN connection is not relevant to VPC peering.
Check the internet gateway configuration
Why it's wrong here
Internet gateway is not used in VPC peering.
Common exam traps
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Real-world example
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
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related ANS-C01 ACL questions on filtering logic and placement.
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FAQ
Network Management and Operations — This question tests Network Management and Operations — Standard ACLs match source addresses..
The correct answer is: Check security group and network ACL rules — Option A is correct because security group rules and NACLs can block traffic even if routes are correct. Option B is wrong because DNS resolution is not related to basic connectivity. Option C is wrong because internet gateway is not involved in VPC peering. Option D is wrong because VPN connection is a different service.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related ANS-C01 ACL questions on filtering logic and placement.
Standard ACLs match source addresses.
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Last reviewed: Jun 20, 2026
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