easyMultiple ChoiceObjective-mapped
300-410 Practice Question: Which statement is true about the implicit deny…
Which statement is true about the implicit deny any at the end of an IPv4 ACL?
⚠ Common exam trap
Cisco often tests the misconception that the implicit deny any can be removed or that it only applies to specific protocols, when in fact it is a permanent, protocol-agnostic rule that denies all unmatched traffic.
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
✓
It denies all traffic not explicitly permitted and is always present.
Every IPv4 ACL has an implicit deny any statement at the end that denies all traffic not explicitly permitted by earlier entries. This implicit rule is always present and cannot be removed, ensuring that only traffic matching a permit entry is allowed through the ACL.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
It can be overridden by adding a permit any at the end.
Why it's wrong here
A permit any entry will match before the implicit deny, effectively overriding it.
- ✗
It is invisible and applies only to TCP traffic.
Why it's wrong here
The implicit deny applies to all IP traffic for extended ACLs.
- ✗
It is always present and cannot be removed or overridden.
Why it's wrong here
It can be overridden by a permit any entry placed before it.
- ✓
It denies all traffic not explicitly permitted and is always present.
Why this is correct
The implicit deny any is a fundamental property of Cisco ACLs.
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Same concept, more angles
1 more way this is tested on 300-410
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. What is the default behavior of an IPv4 access control list (ACL) when no explicit permit or deny statement matches a packet?
easy- A.The packet is permitted.
- ✓ B.The packet is denied.
- C.The packet is logged and then permitted.
- D.The ACL is ignored and the packet is forwarded.
Why B: 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.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.