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300-410 Practice Question: Examine the following IPv6 ACL applied to an…
Examine the following IPv6 ACL applied to an interface:
ipv6 access-list FILTER
permit ipv6 any any fragments deny ipv6 any any interface GigabitEthernet0/1
ipv6 traffic-filter FILTER in
What is the effect of this configuration?
⚠ Common exam trap
Cisco often tests the misconception that 'permit ipv6 any any' without the 'fragments' keyword matches all packets, but here the 'fragments' keyword narrows the match, causing candidates to overlook the sequential processing of ACL entries and incorrectly assume all traffic is permitted.
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
✓
Only fragmented IPv6 packets are permitted; all other IPv6 traffic is denied.
The ACL explicitly permits only fragmented IPv6 packets via the 'permit ipv6 any any fragments' statement, while the subsequent 'deny ipv6 any any' statement denies all other IPv6 traffic. Since ACLs are processed sequentially, the permit for fragments is evaluated first, allowing only fragmented packets; all non-fragmented packets are then denied by the second entry.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
All IPv6 traffic is permitted because the permit statement matches any packet.
Why it's wrong here
The permit statement matches only fragmented packets because the fragments keyword restricts it; non-fragmented IPv6 traffic falls through to the deny statement. It is tempting because 'permit ipv6 any any' looks like a blanket permit, but the fragments keyword narrows it to fragments only, so unfragmented traffic is dropped.
- ✓
Only fragmented IPv6 packets are permitted; all other IPv6 traffic is denied.
Why this is correct
The ACL permits any IPv6 packet carrying a Fragment header, then denies everything else. Because the permit entry matches only fragments, non-fragmented traffic falls through to the deny, so only fragmented IPv6 packets pass inbound on GigabitEthernet0/1.
- ✗
The ACL is invalid because 'fragments' cannot be used with 'any any'.
Why it's wrong here
The fragments keyword is valid with any any in an IPv6 ACL; it matches all fragmented packets regardless of source or destination. It is tempting to assume the combination is syntactically illegal, but Cisco IOS accepts it. The ACL is valid, so the real effect is that only fragments are permitted.
- ✗
The interface command is missing the 'ipv6 enable' prerequisite.
Why it's wrong here
The ipv6 traffic-filter command applies the ACL without requiring ipv6 enable; that command only enables IPv6 processing for link-local addressing on interfaces lacking a global address. It is tempting because ipv6 enable is often configured alongside IPv6 features, but it is not a prerequisite for applying an ACL here.
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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.