The answer is that the ACL is applied to the wrong interface. When an ACL is placed on an interface that does not carry the traffic you intend to filter, the packets never encounter the ACL, so the hardware counters never increment from zero. This is a fundamental concept in Cisco IOS and NX-OS: ACLs must be applied either inbound or outbound on the specific interface where the relevant traffic actually flows. On the Cisco DCCOR / CCNP Data Center Core 350-601 exam, this scenario tests your understanding of ACL placement versus ACL syntax—a common trap is to assume a misconfigured permit or deny statement, but the counters staying at zero always point to a traffic-path issue, not a logic error. A quick memory tip: "Zero matches means zero traffic hits the ACL, so check the interface, not the rules."
350-601 Security Practice Question
This 350-601 practice question tests your understanding of security. 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.
Exhibit
Refer to the exhibit.
! Nexus 9000 ACL configuration
ip access-list BLOCK_MGMT
10 permit tcp host 10.10.1.100 192.168.1.0 0.0.0.255 eq 22
20 deny ip 10.10.0.0 0.0.255.255 192.168.1.0 0.0.0.255
30 permit ip any any
interface Ethernet1/1
ip access-group BLOCK_MGMT in
description Management access to servers
! Output of 'show ip access-list BLOCK_MGMT'
IP access list BLOCK_MGMT
statistics per-entry
10 permit tcp host 10.10.1.100 192.168.1.0 0.0.0.255 eq 22 (0 matches)
20 deny ip 10.10.0.0 0.0.255.255 192.168.1.0 0.0.0.255 (0 matches)
30 permit ip any any (0 matches)
A network administrator implements the ACL shown. After verifying the ACL statistics, all counters show 0 matches. What is the most likely cause?
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.
Refer to the exhibit.
! Nexus 9000 ACL configuration
ip access-list BLOCK_MGMT
10 permit tcp host 10.10.1.100 192.168.1.0 0.0.0.255 eq 22
20 deny ip 10.10.0.0 0.0.255.255 192.168.1.0 0.0.0.255
30 permit ip any any
interface Ethernet1/1
ip access-group BLOCK_MGMT in
description Management access to servers
! Output of 'show ip access-list BLOCK_MGMT'
IP access list BLOCK_MGMT
statistics per-entry
10 permit tcp host 10.10.1.100 192.168.1.0 0.0.0.255 eq 22 (0 matches)
20 deny ip 10.10.0.0 0.0.255.255 192.168.1.0 0.0.0.255 (0 matches)
30 permit ip any any (0 matches)
A
The ACL entries are in the wrong order.
Why wrong: Order is proper: permit SSH first, deny rest, then permit all.
B
The ACL is applied to the wrong interface.
Ethernet1/1 is a management interface; production traffic likely uses other interfaces.
C
The 'permit ip any any' entry causes all traffic to be permitted before inspection.
Why wrong: Sequence number 30 is last; it would only match after previous entries are evaluated.
D
The ACL is applied outbound instead of inbound.
Why wrong: The configuration shows 'in', so it is inbound.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The ACL is applied to the wrong interface.
Option B is correct because if the ACL is applied to the wrong interface, traffic never traverses that interface, so the ACL counters remain at 0. ACLs must be applied to the interface where traffic enters (inbound) or exits (outbound) the device; applying to an interface that does not carry the relevant traffic results in no matches.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 ACL entries are in the wrong order.
Why it's wrong here
Order is proper: permit SSH first, deny rest, then permit all.
✓
The ACL is applied to the wrong interface.
Why this is correct
Ethernet1/1 is a management interface; production traffic likely uses other interfaces.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The 'permit ip any any' entry causes all traffic to be permitted before inspection.
Why it's wrong here
Sequence number 30 is last; it would only match after previous entries are evaluated.
✗
The ACL is applied outbound instead of inbound.
Why it's wrong here
The configuration shows 'in', so it is inbound.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that ACL counters being 0 is always due to a missing 'permit ip any any' or wrong entry order, but the real trap is that the ACL may simply not be processing any traffic because it is applied to the wrong interface or direction.
Trap categories for this question
Command / output trap
The configuration shows 'in', so it is inbound.
Detailed technical explanation
How to think about this question
ACL counters increment per packet that matches an entry; if the ACL is applied to an interface that does not carry the expected traffic (e.g., applied to GigabitEthernet0/1 but traffic flows through GigabitEthernet0/2), the counters stay at 0. This is a common troubleshooting step: verifying the interface and direction with 'show ip interface' or 'show running-config interface' to confirm the ACL is correctly placed. In real-world scenarios, misapplied ACLs can lead to undetected security gaps or unintended traffic flow.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Security — This question tests Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The ACL is applied to the wrong interface. — Option B is correct because if the ACL is applied to the wrong interface, traffic never traverses that interface, so the ACL counters remain at 0. ACLs must be applied to the interface where traffic enters (inbound) or exits (outbound) the device; applying to an interface that does not carry the relevant traffic results in no matches.
What should I do if I get this 350-601 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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?
Read the scenario before looking for a memorised answer.
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