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 on Router R1:
R1# show ip access-lists
Extended IP access list 140
10 deny tcp any host 10.1.1.1 eq 23 (15 matches)
20 permit tcp any host 10.1.1.1 eq 22 (20 matches)
30 permit ip any any (5 matches)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Telnet to 10.1.1.1 is being denied, which may be intentional.
Option B is correct because the ACL explicitly denies TCP traffic to host 10.1.1.1 on port 23 (Telnet) with line 10, and the match count of 15 confirms that Telnet attempts are being blocked. While this may be intentional to enforce secure management via SSH (permitted on port 22), the question asks for the problem, and the output shows Telnet is being denied. The ACL does not block SSH (line 20 permits it), so the issue is specifically that Telnet access is denied.
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.
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that a 'permit ip any any' at the end of an ACL overrides earlier deny statements, but candidates must remember that ACLs are processed sequentially and the first match wins.
Detailed technical explanation
How to think about this question
Access control lists (ACLs) are processed top-down, and the first matching entry determines the action; line 10 (deny) for Telnet will always match before line 30 (permit ip any any) for Telnet traffic to 10.1.1.1. The match counters increment only when the ACL is applied to an interface (inbound or outbound) and traffic is evaluated, confirming the ACL is active. In real-world scenarios, this ACL configuration is common to block insecure Telnet while allowing SSH for secure remote management, but the question highlights that Telnet is explicitly denied.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
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: Telnet to 10.1.1.1 is being denied, which may be intentional. — Option B is correct because the ACL explicitly denies TCP traffic to host 10.1.1.1 on port 23 (Telnet) with line 10, and the match count of 15 confirms that Telnet attempts are being blocked. While this may be intentional to enforce secure management via SSH (permitted on port 22), the question asks for the problem, and the output shows Telnet is being denied. The ACL does not block SSH (line 20 permits it), so the issue is specifically that Telnet access is denied.
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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Question Discussion
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