- A
Strict uRPF is enabled, so the router will drop packets if the source address is not in the routing table or if the best return path is not through the receiving interface.
Correct. Strict uRPF requires both a matching route and that the interface used to reach the source is the same as the receiving interface.
- B
Strict uRPF is enabled, but it only checks if the source address is in the routing table, regardless of interface.
Why wrong: Incorrect. Strict uRPF checks both the route and the interface; loose uRPF only checks the route.
- C
Loose uRPF is enabled, which only checks if the source address is in the routing table.
Why wrong: Incorrect. The output explicitly says 'strict'.
- D
uRPF is disabled on this interface.
Why wrong: Incorrect. The output shows it is enabled with strict mode.
300-410 IPv6 Traffic Filtering and uRPF Practice Question
This 300-410 practice question tests your understanding of ipv6 traffic filtering and urpf. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
A network engineer runs the following command to verify IPv6 uRPF operation:
R1# show ipv6 interface GigabitEthernet0/0 | include verify
IPv6 verify source: strict
What does this output indicate?
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
Strict uRPF is enabled, so the router will drop packets if the source address is not in the routing table or if the best return path is not through the receiving interface.
The output 'IPv6 verify source: strict' indicates that strict unicast Reverse Path Forwarding (uRPF) is enabled on the interface. Strict uRPF verifies that the source IPv6 address of an incoming packet is reachable via the routing table AND that the best return path to that source uses the same interface on which the packet was received. If either condition fails, the packet is dropped. This matches option A exactly.
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.
- ✓
Strict uRPF is enabled, so the router will drop packets if the source address is not in the routing table or if the best return path is not through the receiving interface.
Why this is correct
Correct. Strict uRPF requires both a matching route and that the interface used to reach the source is the same as the receiving interface.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Strict uRPF is enabled, but it only checks if the source address is in the routing table, regardless of interface.
Why it's wrong here
Incorrect. Strict uRPF checks both the route and the interface; loose uRPF only checks the route.
- ✗
Loose uRPF is enabled, which only checks if the source address is in the routing table.
Why it's wrong here
Incorrect. The output explicitly says 'strict'.
- ✗
uRPF is disabled on this interface.
Why it's wrong here
Incorrect. The output shows it is enabled with strict mode.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between strict and loose uRPF by showing the 'verify source' output and expecting candidates to remember that 'strict' requires both a routing table match and the correct incoming interface, while 'loose' only requires the source to be in the routing table.
Trap categories for this question
Command / output trap
Incorrect. The output explicitly says 'strict'.
Detailed technical explanation
How to think about this question
Strict uRPF relies on the Forwarding Information Base (FIB) to perform the source address lookup and interface check. In IPv6, the command 'ipv6 verify unicast source reachable-via rx' (or 'strict') enables this feature. A real-world scenario where strict uRPF is critical is in mitigating spoofed IPv6 traffic on edge interfaces facing customers, ensuring that only traffic with legitimate source addresses from that subnet is accepted, preventing reflection attacks.
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 practitioner preparing for the 300-410 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
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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: Strict uRPF is enabled, so the router will drop packets if the source address is not in the routing table or if the best return path is not through the receiving interface. — The output 'IPv6 verify source: strict' indicates that strict unicast Reverse Path Forwarding (uRPF) is enabled on the interface. Strict uRPF verifies that the source IPv6 address of an incoming packet is reachable via the routing table AND that the best return path to that source uses the same interface on which the packet was received. If either condition fails, the packet is dropped. This matches option A exactly.
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.
About these practice questions
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Last reviewed: Jul 4, 2026
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