- A
All IPv6 traffic is permitted because the permit statement matches any packet.
Why wrong: The 'fragments' keyword matches only non-initial fragments; initial and non-fragmented packets are not matched by this entry.
- B
Only fragmented IPv6 packets are permitted; all other IPv6 traffic is denied.
The first ACE permits only fragments; the second denies everything else, so only fragments pass.
- C
The ACL is invalid because 'fragments' cannot be used with 'any any'.
Why wrong: The 'fragments' keyword is valid with IPv6 ACLs and can be used with any source/destination.
- D
The interface command is missing the 'ipv6 enable' prerequisite.
Why wrong: The 'ipv6 traffic-filter' command does not require 'ipv6 enable' on the interface; it works as long as IPv6 is configured.
Quick Answer
The correct answer is that only fragmented IPv6 packets are permitted while all other IPv6 traffic is denied. This occurs because the ACL processes entries sequentially: the first line, permit ipv6 any any fragments, explicitly matches and allows only IPv6 packets that are fragments, and the subsequent deny ipv6 any any statement catches and blocks every other IPv6 packet, including non-fragmented ones. On the Cisco CCNP ENARSI 300-410 exam, this question tests your understanding of how the fragments keyword behaves in IPv6 ACLs—a common trap is assuming the permit line allows all traffic, but the fragments keyword restricts it solely to fragmented packets. Remember that in IPv6, unlike IPv4, the fragments keyword does not match the first fragment of a fragmented packet; it only matches non-initial fragments. A useful memory tip: “Fragments first, then deny the rest” — the permit for fragments acts as a narrow exception, and the deny is the default gate for everything else.
300-410 IPv6 Traffic Filtering and uRPF Practice Question
This 300-410 practice question tests your understanding of ipv6 traffic filtering and urpf. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
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?
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.
Option B is correct because 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.
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.
- ✗
All IPv6 traffic is permitted because the permit statement matches any packet.
Why it's wrong here
The 'fragments' keyword matches only non-initial fragments; initial and non-fragmented packets are not matched by this entry.
- ✓
Only fragmented IPv6 packets are permitted; all other IPv6 traffic is denied.
Why this is correct
The first ACE permits only fragments; the second denies everything else, so only fragments pass.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The ACL is invalid because 'fragments' cannot be used with 'any any'.
Why it's wrong here
The 'fragments' keyword is valid with IPv6 ACLs and can be used with any source/destination.
- ✗
The interface command is missing the 'ipv6 enable' prerequisite.
Why it's wrong here
The 'ipv6 traffic-filter' command does not require 'ipv6 enable' on the interface; it works as long as IPv6 is configured.
Common exam traps
Common exam trap: answer the scenario, not the keyword
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.
Trap categories for this question
Keyword trap
The 'fragments' keyword matches only non-initial fragments; initial and non-fragmented packets are not matched by this entry.
Command / output trap
The 'ipv6 traffic-filter' command does not require 'ipv6 enable' on the interface; it works as long as IPv6 is configured.
Detailed technical explanation
How to think about this question
In IPv6, fragmentation is handled by the source host using the Fragment Header (RFC 2460), and the 'fragments' keyword in an ACL matches packets that contain this header. This configuration is often used in security policies to allow fragmented packets (which may be needed for certain protocols like DNS or ICMPv6) while blocking all other traffic, but it can inadvertently permit malicious fragments that evade stateful inspection. A real-world scenario is when an attacker sends fragmented packets to bypass ACLs that only inspect the first fragment, making this a risky configuration unless combined with deeper inspection.
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.
What to study next
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FAQ
Questions learners often ask
What does this 300-410 question test?
IPv6 Traffic Filtering and uRPF — This question tests IPv6 Traffic Filtering and uRPF — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Only fragmented IPv6 packets are permitted; all other IPv6 traffic is denied. — Option B is correct because 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.
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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Last reviewed: Jun 24, 2026
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.
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