CCNA IP Routing Practice Question
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.
⚠ Common exam trap
A common trap is to enable OSPFv3 only on the link interfaces or only on the loopbacks. Remember that OSPFv3 must be enabled on every interface that needs to be advertised or that participates in neighbor discovery. Also, note that OSPFv3 uses 'ipv6 ospf <process-id> area <area-id>' under the interface, not the network statement used in OSPFv2.
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
✓
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.
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 the loopback interfaces is insufficient because OSPFv3 requires adjacency over a real link; loopbacks have no neighbor attached, so no hello packets are exchanged and no OSPFv3 neighbor relationship forms. The transit interfaces (R1's GigabitEthernet0/0 and R2's GigabitEthernet0/1) are what connect the two routers, and without enabling OSPFv3 on those links, the routers cannot discover each other or exchange route information. The loopback prefixes would remain local and unreachable from the peer.
- ✗
Enable OSPFv3 on R1's GigabitEthernet0/0 and R2's GigabitEthernet0/1 only, without loopbacks.
Why it's wrong here
This configuration forms an OSPFv3 adjacency between R1 and R2 on the GigabitEthernet link, but it fails to advertise the loopback prefixes into the OSPFv3 domain. In OSPFv3, each interface must be explicitly enabled under the routing process; enabling only the transit interfaces means the loopback networks are not inserted into the link-state database. As a result, R1 and R2 will have OSPF routes for the point-to-point link, but they will have no route to each other's Loopback0, making the loopback addresses unreachable and defeating the purpose of advertising them.
- ✗
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?”
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
Go deeper
Related to this question
Learn chapter
OSPFv3 Single-Area Configuration for IPv6
Key term
OSPFv3
OSPFv3 is the version of the Open Shortest Path First routing protocol that supports IPv6 networks, enabling routers to exchange routing information for IPv6 addresses.
Key term
CAN
A CAN (Controller Area Network) is a robust vehicle bus standard designed to allow microcontrollers and devices to communicate with each other without a host computer.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.