- A
deny ipv6 any 2001:db8:1::/48
This correctly denies all IPv6 traffic from any source to the specified destination prefix.
- B
deny ipv6 2001:db8:1::/48 any
Why wrong: This denies traffic from the specified source to any destination, which is the opposite of what is asked.
- C
deny ipv6 any host 2001:db8:1::1
Why wrong: This denies traffic to a single host, not the /48 prefix.
- D
deny ipv6 2001:db8:1::/48 2001:db8:1::/48
Why wrong: This denies traffic from the prefix to itself, which is not the intended behavior.
Question 1,089 of 2,152
IPv6 ACL Deny Destination Prefix
This 300-410 practice question tests your understanding of ipv6 traffic filtering and urpf. 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.
Which IPv6 access-list entry will deny traffic from any source to the destination prefix 2001:db8:1::/48?
Quick Answer
The correct answer is deny ipv6 any 2001:db8:1::/48. This entry is correct because in an IPv6 ACL, the deny keyword is followed by the protocol (ipv6), then the source, and then the destination prefix; the any keyword matches all source addresses, and the destination prefix 2001:db8:1::/48 is specified directly after it, exactly as required to block traffic to that entire subnet. On the Cisco CCNP ENARSI 300-410 exam, this tests your understanding of IPv6 ACL syntax and the order of operands, which is a common pitfall—many candidates mistakenly place the destination before the source or forget the protocol keyword. A frequent trap is confusing the IPv4 ACL structure, where the source comes first, with the identical IPv6 order, but the key is to remember that both IPv4 and IPv6 ACLs follow the same sequence: action, protocol, source, destination. For a memory tip, think “Deny any to the prefix” as the natural flow: deny ipv6 any [prefix].
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
✓
deny ipv6 any 2001:db8:1::/48
Option A is correct because the IPv6 access-list entry 'deny ipv6 any 2001:db8:1::/48' uses the correct syntax: the source is 'any' (all traffic), and the destination is the prefix 2001:db8:1::/48, which matches all addresses within that /48 range. This entry denies traffic from any source to the entire destination prefix, as required by the question.
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.
- ✓
deny ipv6 any 2001:db8:1::/48
Why this is correct
This correctly denies all IPv6 traffic from any source to the specified destination prefix.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
deny ipv6 2001:db8:1::/48 any
Why it's wrong here
This denies traffic from the specified source to any destination, which is the opposite of what is asked.
- ✗
deny ipv6 any host 2001:db8:1::1
Why it's wrong here
This denies traffic to a single host, not the /48 prefix.
- ✗
deny ipv6 2001:db8:1::/48 2001:db8:1::/48
Why it's wrong here
This denies traffic from the prefix to itself, which is not the intended behavior.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the order of source and destination in ACL entries, where candidates mistakenly reverse them (as in Option B) or use a host keyword instead of a prefix (as in Option C), thinking it matches a range.
Detailed technical explanation
How to think about this question
In IPv6 ACLs, the prefix length (e.g., /48) defines a range of addresses; the ACL matches any address within that prefix. The 'any' keyword is a shorthand for the IPv6 unspecified address (::/0) for source or destination. This is analogous to IPv4 ACLs but uses IPv6-specific syntax, and the order of entries matters because ACLs are processed sequentially until a match is found.
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: deny ipv6 any 2001:db8:1::/48 — Option A is correct because the IPv6 access-list entry 'deny ipv6 any 2001:db8:1::/48' uses the correct syntax: the source is 'any' (all traffic), and the destination is the prefix 2001:db8:1::/48, which matches all addresses within that /48 range. This entry denies traffic from any source to the entire destination prefix, as required by the question.
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: Jul 4, 2026
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