easyMultiple Choice
300-410 Practice Question: By default in Cisco IOS-XE, what is the behavior…
By default in Cisco IOS-XE, what is the behavior of an IPv4 ACL when no entries match and the ACL is applied to an inbound interface?
⚠ Common exam trap
Cisco often tests the implicit deny any behavior by presenting scenarios where an ACL has no matching entries, leading candidates to mistakenly think the packet is permitted or forwarded based on routing.
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 packet is denied.
By default, Cisco IOS-XE applies an implicit 'deny any' statement at the end of every IPv4 ACL. If no entries match the packet, the implicit deny triggers, and the packet is dropped. This behavior is consistent for ACLs applied to inbound interfaces, ensuring that only explicitly permitted traffic is allowed.
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
Cisco IOS-XE appends an implicit deny any to every IPv4 ACL, so unmatched inbound packets are dropped, not permitted. The temptation is that an empty or unapplied ACL passes traffic, and a permit any would be needed to achieve that, but the stem specifies an ACL with no matching entry.
- ✓
The packet is denied.
Why this is correct
An IPv4 ACL carries an implicit deny any at its end, so a packet matching no entry is discarded. Applied inbound, this means unmatched traffic is dropped by default, satisfying the stem's question about default behaviour.
- ✗
The packet is forwarded based on routing table lookup.
Why it's wrong here
Routing table lookup never occurs for a packet denied by the implicit deny any at the end of the inbound ACL; it is discarded before any forwarding decision. It is tempting because forwarding by route lookup is the normal path for permitted traffic, so it would be correct only if an explicit permit statement had matched.
- ✗
The ACL logs the packet and continues.
Why it's wrong here
Logging requires an explicit log keyword on an ACE; the implicit deny-all at the end of every IPv4 ACL neither logs nor continues processing. It is tempting because ACL logging is a real feature, but it must be configured per entry, so it would only be correct where the administrator has deliberately added a logging deny statement.
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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.