- A
Apply an inbound IPv6 access-list on the interface that denies traffic from the source prefix.
Correct. An IPv6 access-list applied inbound on an interface can filter traffic based on source prefix.
- B
Configure a route map that matches the source prefix and sets a BGP community, then apply it inbound on the BGP neighbor to filter the prefix from being advertised.
Correct. This prevents the prefix from being installed in the routing table, effectively blocking traffic sourced from that prefix.
- C
Use the 'ipv6 route' command to install a discard route for the source prefix.
Why wrong: Incorrect. A discard route only affects destination-based forwarding, not source-based filtering. It would drop traffic destined to that prefix, not sourced from it.
- D
Apply an outbound IPv6 access-list on the interface to block traffic from the source prefix.
Why wrong: Incorrect. An outbound access-list filters traffic leaving the interface, but the source prefix is still forwarded until it reaches the egress. Inbound filtering is needed to drop traffic early.
- E
Configure uRPF strict mode on the interface to drop packets from the source prefix if the prefix is not in the FIB.
Why wrong: Incorrect. uRPF drops packets only if the source is not reachable via the incoming interface or not in FIB, but if the prefix is legitimate and reachable, uRPF will not block it.
Quick Answer
The answer is configuring an inbound IPv6 access-list on the interface or applying a route map that matches the source prefix and sets a denied BGP community. These two methods block IPv6 traffic from a specific source prefix without relying on a prefix list, because an access-list filters traffic at the interface level based on source addresses, while BGP community-based filtering uses a route map to tag and deny the prefix at the neighbor inbound stage, preventing its advertisement and subsequent forwarding. On the Cisco CCNP ENARSI 300-410 exam, this tests your ability to distinguish between traffic filtering and routing policy tools—a common trap is confusing route filtering (like distribute-lists) with actual traffic blocking, which requires interface ACLs or community manipulation. Remember the memory tip: “ACL for the wire, community for the peer” to recall that access-lists block traffic directly, while BGP communities block the route from being shared, indirectly stopping traffic.
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.
Which TWO configuration changes will prevent IPv6 traffic from being forwarded from a specific source prefix in a BGP environment without using a prefix list? (Choose TWO.)
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
Apply an inbound IPv6 access-list on the interface that denies traffic from the source prefix.
To block IPv6 traffic from a source prefix, you can use an inbound IPv6 access-list on the interface or leverage BGP path filtering with a route map that matches the source prefix and sets a community that is denied. Another method is to use a route policy to filter the prefix from being installed in the routing table, but that affects routing, not traffic filtering. The question asks for traffic filtering without a prefix list (but an access-list is allowed). Using 'ipv6 access-list' and applying it inbound is valid. Also, using BGP community-based filtering can block traffic at the edge.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Apply an inbound IPv6 access-list on the interface that denies traffic from the source prefix.
Why this is correct
Correct. An IPv6 access-list applied inbound on an interface can filter traffic based on source prefix.
Related concept
OSPF neighbours must agree on key parameters.
- ✓
Configure a route map that matches the source prefix and sets a BGP community, then apply it inbound on the BGP neighbor to filter the prefix from being advertised.
Why this is correct
Correct. This prevents the prefix from being installed in the routing table, effectively blocking traffic sourced from that prefix.
Related concept
OSPF neighbours must agree on key parameters.
- ✗
Use the 'ipv6 route' command to install a discard route for the source prefix.
Why it's wrong here
Incorrect. A discard route only affects destination-based forwarding, not source-based filtering. It would drop traffic destined to that prefix, not sourced from it.
- ✗
Apply an outbound IPv6 access-list on the interface to block traffic from the source prefix.
Why it's wrong here
Incorrect. An outbound access-list filters traffic leaving the interface, but the source prefix is still forwarded until it reaches the egress. Inbound filtering is needed to drop traffic early.
- ✗
Configure uRPF strict mode on the interface to drop packets from the source prefix if the prefix is not in the FIB.
Why it's wrong here
Incorrect. uRPF drops packets only if the source is not reachable via the incoming interface or not in FIB, but if the prefix is legitimate and reachable, uRPF will not block it.
Common exam traps
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
- OSPF neighbours must agree on key parameters.
- Router ID selection can affect neighbour relationships and LSDB output.
- OSPF cost influences the preferred path.
- A route can appear in OSPF information but not become the installed route.
TExam Day Tips
- Check area mismatch first when OSPF adjacency fails.
- Review passive interfaces when a network is advertised but no neighbour forms.
- Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
Got this wrong? Here's your next step.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
- →
IPv6 Traffic Filtering and uRPF — study guide chapter
Learn the concepts, then practise the questions
- →
IPv6 Traffic Filtering and uRPF practice questions
Targeted practice on this topic area only
- →
All 300-410 questions
2,152 questions across all exam domains
- →
Cisco CCNP ENARSI 300-410 study guide
Full concept coverage aligned to exam objectives
- →
300-410 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related 300-410 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Layer 3 Technologies practice questions
Practise 300-410 questions linked to Layer 3 Technologies.
EIGRP Troubleshooting practice questions
Practise 300-410 questions linked to EIGRP Troubleshooting.
OSPF Troubleshooting (v2/v3) practice questions
Practise 300-410 questions linked to OSPF Troubleshooting (v2/v3).
BGP Troubleshooting practice questions
Practise 300-410 questions linked to BGP Troubleshooting.
Route Redistribution practice questions
Practise 300-410 questions linked to Route Redistribution.
Policy-Based Routing (PBR) practice questions
Practise 300-410 questions linked to Policy-Based Routing (PBR).
VRF-Lite practice questions
Practise 300-410 questions linked to VRF-Lite.
Route Maps and Route Filtering practice questions
Practise 300-410 questions linked to Route Maps and Route Filtering.
Administrative Distance practice questions
Practise 300-410 questions linked to Administrative Distance.
Route Summarization practice questions
Practise 300-410 questions linked to Route Summarization.
Bidirectional Forwarding Detection (BFD) practice questions
Practise 300-410 questions linked to Bidirectional Forwarding Detection (BFD).
VPN Technologies practice questions
Practise 300-410 questions linked to VPN Technologies.
Practice this exam
Start a free 300-410 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
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 — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: Apply an inbound IPv6 access-list on the interface that denies traffic from the source prefix. — To block IPv6 traffic from a source prefix, you can use an inbound IPv6 access-list on the interface or leverage BGP path filtering with a route map that matches the source prefix and sets a community that is denied. Another method is to use a route policy to filter the prefix from being installed in the routing table, but that affects routing, not traffic filtering. The question asks for traffic filtering without a prefix list (but an access-list is allowed). Using 'ipv6 access-list' and applying it inbound is valid. Also, using BGP community-based filtering can block traffic at the edge.
What should I do if I get this 300-410 question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jun 18, 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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.