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IPv4 Access Control Lists →mediumMultiple ChoiceObjective-mapped

300-410 IPv4 Access Control Lists Practice Question

This 300-410 practice question tests your understanding of ipv4 access control lists. 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 runs the following command to troubleshoot an IPv4 Access Control Lists issue:

R1# debug ip packet 100 detail
IP packet debugging is on for access list 100
*Mar  1 00:12:34.567: IP: s=10.1.1.1 (GigabitEthernet0/0), d=10.2.2.2, len 100, proto UDP, flags 0x0, sport 12345, dport 80, access list 100: matched line 10 permit udp host 10.1.1.1 host 10.2.2.2 eq 80
*Mar  1 00:12:35.123: IP: s=10.1.1.1 (GigabitEthernet0/0), d=10.2.2.2, len 100, proto TCP, flags 0x2, sport 12346, dport 443, access list 100: matched line 
20 deny tcp host 10.1.1.1 host 10.2.2.2 eq 443
*Mar  1 00:12:35.124: IP: s=10.1.1.1 (GigabitEthernet0/0), d=10.2.2.2, len 100, proto TCP, flags 0x10, sport 12346, dport 443, access list 100: matched line 
20 deny tcp host 10.1.1.1 host 10.2.2.2 eq 443

What does this output indicate?

Question 1mediummultiple choice
Study the full ACL explanation →

Answer choices

Why each option matters

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 inbound on GigabitEthernet0/0 and is permitting UDP traffic to port 80 while denying TCP traffic to port 443.

The debug output shows packets entering GigabitEthernet0/0 (source interface) and matching ACL 100. The first packet (UDP to port 80) matches line 10 (permit), while subsequent TCP packets to port 443 match line 20 (deny). Since the source interface is the inbound interface, the ACL is applied inbound. This confirms Option A: the ACL permits UDP to port 80 and denies TCP to port 443.

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 is applied inbound on GigabitEthernet0/0 and is permitting UDP traffic to port 80 while denying TCP traffic to port 443.

    Why this is correct

    The debug output shows that UDP traffic to port 80 matches line 10 (permit) and TCP traffic to port 443 matches line 20 (deny).

    Related concept

    Read the scenario before looking for a memorised answer.

  • ✗

    The ACL is applied outbound on GigabitEthernet0/0 and is permitting all traffic.

    Why it's wrong here

    The debug shows deny matches, not just permit.

  • ✗

    The ACL is misconfigured because TCP traffic to port 443 should be permitted.

    Why it's wrong here

    The ACL is correctly denying TCP to port 443 as per the debug.

  • ✗

    The ACL is not applied to any interface because debug ip packet shows only the ACL number.

    Why it's wrong here

    The debug shows the interface (GigabitEthernet0/0) and the ACL matches.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Cisco often tests the ability to distinguish inbound vs. outbound ACL application by interpreting the source and destination IP addresses in debug output, where the trap is that candidates mistakenly assume the ACL is outbound because the destination IP is different, ignoring that the source interface reveals the direction.

Trap categories for this question

  • Command / output trap

    The debug shows deny matches, not just permit.

Detailed technical explanation

How to think about this question

The 'debug ip packet' command with an ACL number filters only packets that match the specified ACL, but the interface is always displayed in the output as the source (s=) or destination (d=) IP address, which corresponds to the inbound or outbound interface. In this case, the source IP 10.1.1.1 is on GigabitEthernet0/0, indicating the ACL is applied inbound. The flags field (e.g., 0x2 for SYN, 0x10 for ACK) shows that the ACL processes all TCP segments, including SYN and ACK, which is critical for stateful inspection scenarios.

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.

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FAQ

Questions learners often ask

What does this 300-410 question test?

IPv4 Access Control Lists — This question tests IPv4 Access Control Lists — 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 inbound on GigabitEthernet0/0 and is permitting UDP traffic to port 80 while denying TCP traffic to port 443. — The debug output shows packets entering GigabitEthernet0/0 (source interface) and matching ACL 100. The first packet (UDP to port 80) matches line 10 (permit), while subsequent TCP packets to port 443 match line 20 (deny). Since the source interface is the inbound interface, the ACL is applied inbound. This confirms Option A: the ACL permits UDP to port 80 and denies TCP to port 443.

What should I do if I get this 300-410 question wrong?

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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Last reviewed: Jun 24, 2026

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This 300-410 practice question is part of Courseiva's free Cisco 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 300-410 exam.