This 200-301 practice question tests your understanding of ip routing. 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.
Network Topology
You are connected to R1 via console. Configure OSPFv3 for IPv6 on R1 and R2 so that IPv6 loopback interfaces on both routers can communicate. R1's GigabitEthernet0/0 and R2's GigabitEthernet0/1 are directly connected. Ensure OSPFv3 is enabled on the correct interfaces and verify neighbors and routes.
R1# show running-config | section ipv6
ipv6 unicast-routing
!
interface Loopback0
ipv6 address 2001:db8:1::1/64
!
interface GigabitEthernet0/0
ipv6 address 2001:db8:12::1/64
no shutdown
!
interface GigabitEthernet0/1
ipv6 address 2001:db8:13::1/64
no shutdown
R2# show running-config | section ipv6
ipv6 unicast-routing
!
interface Loopback0
ipv6 address 2001:db8:2::1/64
!
interface GigabitEthernet0/0
ipv6 address 2001:db8:23::1/64
no shutdown
!
interface GigabitEthernet0/1
ipv6 address 2001:db8:12::2/64
no shutdown
A
Enable OSPFv3 on R1's GigabitEthernet0/0 and Loopback0, and on R2's GigabitEthernet0/1 and Loopback0.
OSPFv3 must be enabled on the interfaces that participate in the routing process. On R1, GigabitEthernet0/0 connects to R2, and Loopback0 is the source of the IPv6 prefix to be advertised. Similarly, on R2, GigabitEthernet0/1 connects to R1, and Loopback0 advertises its IPv6 prefix. Enabling OSPFv3 on these interfaces allows neighbor discovery and route exchange.
B
Enable OSPFv3 only on the loopback interfaces of both routers.
Why wrong: Enabling OSPFv3 only on loopback interfaces does not establish a neighbor adjacency because the link between the routers (GigabitEthernet0/0 and GigabitEthernet0/1) is not participating in OSPFv3. Without adjacency, no routes are exchanged.
C
Enable OSPFv3 on R1's GigabitEthernet0/0 and R2's GigabitEthernet0/1 only, without loopbacks.
Why wrong: While this enables neighbor adjacency on the link, the loopback interfaces are not advertised into OSPFv3. Without advertising the loopbacks, their IPv6 prefixes are not in the routing table, so they cannot communicate.
D
Enable OSPFv3 on R1's Loopback0 and R2's GigabitEthernet0/1 only.
Why wrong: This configuration is asymmetric and incomplete. R1's link interface (GigabitEthernet0/0) is not enabled, so R1 cannot form an adjacency. R2's loopback is not enabled, so its prefix is not advertised. No neighbor adjacency forms, and routes are not exchanged.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Enable OSPFv3 on R1's GigabitEthernet0/0 and Loopback0, and on R2's GigabitEthernet0/1 and Loopback0.
The issue is that OSPFv3 is not enabled on the interfaces. On R1, OSPFv3 must be enabled on GigabitEthernet0/0 (the link to R2) and Loopback0 (to advertise the loopback). On R2, OSPFv3 must be enabled on GigabitEthernet0/1 (the link to R1) and Loopback0. After enabling OSPFv3 on the correct interfaces, the neighbor adjacency forms and routes are exchanged.
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.
✓
Enable OSPFv3 on R1's GigabitEthernet0/0 and Loopback0, and on R2's GigabitEthernet0/1 and Loopback0.
Why this is correct
OSPFv3 must be enabled on the interfaces that participate in the routing process. On R1, GigabitEthernet0/0 connects to R2, and Loopback0 is the source of the IPv6 prefix to be advertised. Similarly, on R2, GigabitEthernet0/1 connects to R1, and Loopback0 advertises its IPv6 prefix. Enabling OSPFv3 on these interfaces allows neighbor discovery and route exchange.
Enable OSPFv3 only on the loopback interfaces of both routers.
Why it's wrong here
Enabling OSPFv3 only on loopback interfaces does not establish a neighbor adjacency because the link between the routers (GigabitEthernet0/0 and GigabitEthernet0/1) is not participating in OSPFv3. Without adjacency, no routes are exchanged.
✗
Enable OSPFv3 on R1's GigabitEthernet0/0 and R2's GigabitEthernet0/1 only, without loopbacks.
Why it's wrong here
While this enables neighbor adjacency on the link, the loopback interfaces are not advertised into OSPFv3. Without advertising the loopbacks, their IPv6 prefixes are not in the routing table, so they cannot communicate.
✗
Enable OSPFv3 on R1's Loopback0 and R2's GigabitEthernet0/1 only.
Why it's wrong here
This configuration is asymmetric and incomplete. R1's link interface (GigabitEthernet0/0) is not enabled, so R1 cannot form an adjacency. R2's loopback is not enabled, so its prefix is not advertised. No neighbor adjacency forms, and routes are not exchanged.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓Enable OSPFv3 on R1's GigabitEthernet0/0 and Loopback0, and on R2's GigabitEthernet0/1 and Loopback0.Correct answer▾
Why this is correct
OSPFv3 must be enabled on the interfaces that participate in the routing process. On R1, GigabitEthernet0/0 connects to R2, and Loopback0 is the source of the IPv6 prefix to be advertised. Similarly, on R2, GigabitEthernet0/1 connects to R1, and Loopback0 advertises its IPv6 prefix. Enabling OSPFv3 on these interfaces allows neighbor discovery and route exchange.
✗Enable OSPFv3 only on the loopback interfaces of both routers.Wrong answer — click to see why▾
Why this is wrong here
OSPFv3 requires the link interface to be enabled to form neighbors; loopback-only configuration results in no neighbor relationship.
Why candidates choose this
Candidates may think that since loopbacks are the endpoints, enabling OSPFv3 only on them is sufficient, ignoring the need for adjacency on the transit link.
✗Enable OSPFv3 on R1's GigabitEthernet0/0 and R2's GigabitEthernet0/1 only, without loopbacks.Wrong answer — click to see why▾
Why this is wrong here
OSPFv3 must be enabled on the loopback interfaces to advertise their prefixes; otherwise, they remain unknown to the neighbor.
Why candidates choose this
Candidates might focus only on forming the neighbor adjacency and forget that the loopback prefixes need to be explicitly advertised.
✗Enable OSPFv3 on R1's Loopback0 and R2's GigabitEthernet0/1 only.Wrong answer — click to see why▾
Why this is wrong here
Both routers must have OSPFv3 enabled on the link interface to form an adjacency, and both loopbacks must be enabled to advertise their prefixes.
Why candidates choose this
Candidates may incorrectly think that enabling OSPFv3 on one side of the link is enough, or they may mix up which interfaces need configuration.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
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 200-301 OSPF questions on adjacency and route selection.
IP Routing — This question tests IP Routing — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: Enable OSPFv3 on R1's GigabitEthernet0/0 and Loopback0, and on R2's GigabitEthernet0/1 and Loopback0. — The issue is that OSPFv3 is not enabled on the interfaces. On R1, OSPFv3 must be enabled on GigabitEthernet0/0 (the link to R2) and Loopback0 (to advertise the loopback). On R2, OSPFv3 must be enabled on GigabitEthernet0/1 (the link to R1) and Loopback0. After enabling OSPFv3 on the correct interfaces, the neighbor adjacency forms and routes are exchanged.
What should I do if I get this 200-301 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 200-301 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 →
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.
This 200-301 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 200-301 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.