The answer is that the ACL 110 is not applied to any interface. This is the most likely cause because an ACL, no matter how precisely its access control entries are defined, only filters traffic when it is explicitly applied to an interface in the inbound or outbound direction. The show access-lists command confirms the ACL exists but shows zero matches, while the interface configuration reveals that no access list is set, meaning the router never consults ACL 110 during packet forwarding. On the CCNA 200-301 v2 exam, this scenario tests your understanding that defining an ACL is a separate step from applying it with the ip access-group command under the interface; a common trap is assuming a configured ACL is active by default. Remember the memory tip: "Define it, then assign it—no interface, no filter."
CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. 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.
Exhibit
R1# show ip interface GigabitEthernet0/0
GigabitEthernet0/0 is up, line protocol is up
Internet address is 192.168.1.1/24
Broadcast address is 255.255.255.255
Address determined by setup command
MTU is 1500 bytes
Helper address is not set
Directed broadcast forwarding is disabled
Multicast reserved groups joined: 224.0.0.251 224.0.0.252
Outgoing access list is not set
Inbound access list is not set
Proxy ARP is enabled
Local Proxy ARP is disabled
Refer to the exhibit. A network engineer is troubleshooting an ACL that is not filtering traffic as expected. The engineer runs the show access-lists 110 command and notices that all access control entries (ACEs) show zero matches, even though traffic that should match the permit or deny statements is traversing the network. The engineer then checks the interface configuration. 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.
R1# show ip interface GigabitEthernet0/0
GigabitEthernet0/0 is up, line protocol is up
Internet address is 192.168.1.1/24
Broadcast address is 255.255.255.255
Address determined by setup command
MTU is 1500 bytes
Helper address is not set
Directed broadcast forwarding is disabled
Multicast reserved groups joined: 224.0.0.251 224.0.0.252
Outgoing access list is not set
Inbound access list is not set
Proxy ARP is enabled
Local Proxy ARP is disabled
A
The ACL is applied to the interface in the wrong direction (inbound instead of outbound).
Why wrong: If the ACL were applied in any direction, the output would show an access list number or name, even if it were the wrong direction. Both lines are 'not set', proving that no ACL is assigned.
B
The access-list 110 syntax has incorrect subnet masks causing no matches.
Why wrong: Syntax errors in the ACL entries would not prevent the access list from being applied or shown on the interface. The issue is the absence of any applied ACL.
C
The ACL 110 is not applied to any interface.
The 'Inbound access list is not set' and 'Outgoing access list is not set' lines in the exhibit directly prove that no ACL has been applied to GigabitEthernet0/0. Since ACL 110 exists but isn't attached to any interface, it never processes traffic and shows zero hit counts.
D
The interface GigabitEthernet0/0 is administratively down, preventing ACL processing.
Why wrong: The first line of the exhibit states 'GigabitEthernet0/0 is up, line protocol is up', indicating the interface is operational. An administratively down interface would show 'administratively down, line protocol is down'.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The ACL 110 is not applied to any interface.
The exhibit shows 'Inbound access list is not set' and 'Outgoing access list is not set' under GigabitEthernet0/0. This confirms that no access list has been applied to this interface, so access list 110, though defined, is not filtering any traffic. Zero matches are observed because the ACL is never consulted.
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 ACL is applied to the interface in the wrong direction (inbound instead of outbound).
Why it's wrong here
If the ACL were applied in any direction, the output would show an access list number or name, even if it were the wrong direction. Both lines are 'not set', proving that no ACL is assigned.
✗
The access-list 110 syntax has incorrect subnet masks causing no matches.
Why it's wrong here
Syntax errors in the ACL entries would not prevent the access list from being applied or shown on the interface. The issue is the absence of any applied ACL.
✓
The ACL 110 is not applied to any interface.
Why this is correct
The 'Inbound access list is not set' and 'Outgoing access list is not set' lines in the exhibit directly prove that no ACL has been applied to GigabitEthernet0/0. Since ACL 110 exists but isn't attached to any interface, it never processes traffic and shows zero hit counts.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
The interface GigabitEthernet0/0 is administratively down, preventing ACL processing.
Why it's wrong here
The first line of the exhibit states 'GigabitEthernet0/0 is up, line protocol is up', indicating the interface is operational. An administratively down interface would show 'administratively down, line protocol is down'.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓The ACL 110 is not applied to any interface.Correct answer▾
Why this is correct
The 'Inbound access list is not set' and 'Outgoing access list is not set' lines in the exhibit directly prove that no ACL has been applied to GigabitEthernet0/0. Since ACL 110 exists but isn't attached to any interface, it never processes traffic and shows zero hit counts.
✗The ACL is applied to the interface in the wrong direction (inbound instead of outbound).Wrong answer — click to see why▾
Why this is wrong here
A common mistake is to try to explain zero matches by directional misapplication without first checking whether an ACL is actually present. The exhibit explicitly shows no ACL is bound.
✗The access-list 110 syntax has incorrect subnet masks causing no matches.Wrong answer — click to see why▾
Why this is wrong here
Some candidates fixate on ACL configuration details instead of verifying interface assignment. The output confirms the interface has no ACL, not that an ACL is configured incorrectly.
✗The interface GigabitEthernet0/0 is administratively down, preventing ACL processing.Wrong answer — click to see why▾
Why this is wrong here
Candidates sometimes misread interface status. This output clearly shows the interface is enabled and up, so a down state is not the issue.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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.
Trap categories for this question
Command / output trap
If the ACL were applied in any direction, the output would show an access list number or name, even if it were the wrong direction. Both lines are 'not set', proving that no ACL is assigned.
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
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 200-301 subnetting questions on CIDR, address ranges, and subnet selection.
Network Services and Security — This question tests Network Services and Security — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The ACL 110 is not applied to any interface. — The exhibit shows 'Inbound access list is not set' and 'Outgoing access list is not set' under GigabitEthernet0/0. This confirms that no access list has been applied to this interface, so access list 110, though defined, is not filtering any traffic. Zero matches are observed because the ACL is never consulted.
What should I do if I get this 200-301 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 200-301 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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