300-410 IPv4 Access Control Lists Practice Question
This 300-410 practice question tests your understanding of ipv4 access control lists. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
What is the default behavior of an IPv4 access control list (ACL) when no explicit permit or deny statement matches a packet?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The packet is denied.
By default, IPv4 ACLs have an implicit deny any statement at the end. If a packet does not match any explicit permit or deny entry, the implicit deny any is applied, causing the packet to be dropped. This behavior is fundamental to ACL security, ensuring that only explicitly permitted traffic is allowed.
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 packet is permitted.
Why it's wrong here
Incorrect. The default is to deny traffic that does not match any entry.
✓
The packet is denied.
Why this is correct
Correct. All ACLs have an implicit deny any at the end.
Related concept
Read the scenario before looking for a memorised answer.
✗
The packet is logged and then permitted.
Why it's wrong here
Incorrect. Logging is only done if the 'log' keyword is used, and the default action is deny.
✗
The ACL is ignored and the packet is forwarded.
Why it's wrong here
Incorrect. The ACL is always applied; unmatched packets are denied.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that an ACL with no matching entries will permit traffic by default, or that the ACL is simply ignored, when in fact the implicit deny any silently drops all unmatched packets.
Trap categories for this question
Keyword trap
Incorrect. Logging is only done if the 'log' keyword is used, and the default action is deny.
Detailed technical explanation
How to think about this question
The implicit deny any is automatically appended to every IPv4 ACL, whether standard or extended, and it applies to both inbound and outbound traffic. This default behavior is defined in RFC 1700 and is enforced by Cisco IOS; it means that an ACL with no permit statements will block all traffic. In real-world scenarios, forgetting to add a permit statement for required traffic (e.g., routing protocols or management access) can cause connectivity loss, which is a common troubleshooting issue.
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: The packet is denied. — By default, IPv4 ACLs have an implicit deny any statement at the end. If a packet does not match any explicit permit or deny entry, the implicit deny any is applied, causing the packet to be dropped. This behavior is fundamental to ACL security, ensuring that only explicitly permitted traffic is allowed.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.