CCNA IP Routing Practice Question
Network Topology
You are connected to R1. Configure OSPFv3 for IPv6 on R1 and R2 so that the loopback0 interface on R1 (IPv6 address 2001:db8:1::1/64) can ping the loopback0 interface on R2 (IPv6 address 2001:db8:2::1/64). The routers are connected via their GigabitEthernet0/0 interfaces using IPv6 addresses 2001:db8:12::1/64 (R1) and 2001:db8:12::2/64 (R2). OSPFv3 process ID 100 must be used, and all interfaces must be in area 0.
⚠ Common exam trap
The most common trap is using OSPFv2-style 'network' commands for OSPFv3. Remember that OSPFv3 uses interface-level configuration. Also, ensure all interfaces that need to be advertised (including loopbacks) have OSPFv3 enabled, and that router-ids are unique.
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
✓
R1(config)# ipv6 unicast-routing R1(config)# ipv6 router ospf 100 R1(config-rtr)# router-id 1.1.1.1 R1(config-rtr)# interface gigabitethernet0/0 R1(config-if)# ipv6 ospf 100 area 0 R1(config-if)# interface loopback0 R1(config-if)# ipv6 ospf 100 area 0 R2(config)# ipv6 unicast-routing R2(config)# ipv6 router ospf 100 R2(config-rtr)# router-id 2.2.2.2 R2(config-rtr)# interface gigabitethernet0/0 R2(config-if)# ipv6 ospf 100 area 0 R2(config-if)# interface loopback0 R2(config-if)# ipv6 ospf 100 area 0
OSPFv3 for IPv6 requires enabling IPv6 unicast routing globally and configuring OSPFv3 on interfaces. The missing step was enabling OSPFv3 process 100 and assigning area 0 to the interfaces. On R1, the commands 'ipv6 router ospf 100' and 'router-id 1.1.1.1' create the OSPFv3 process, then 'ipv6 ospf 100 area 0' under each interface enables OSPFv3 on those interfaces. Similar commands on R2 with a unique router-id complete the configuration. Verification with 'show ospfv3 neighbor' should show R2's router-id, and 'show ipv6 route ospf' should display the remote loopback network.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
R1(config)# ipv6 unicast-routing R1(config)# ipv6 router ospf 100 R1(config-rtr)# router-id 1.1.1.1 R1(config-rtr)# interface gigabitethernet0/0 R1(config-if)# ipv6 ospf 100 area 0 R1(config-if)# interface loopback0 R1(config-if)# ipv6 ospf 100 area 0 R2(config)# ipv6 unicast-routing R2(config)# ipv6 router ospf 100 R2(config-rtr)# router-id 2.2.2.2 R2(config-rtr)# interface gigabitethernet0/0 R2(config-if)# ipv6 ospf 100 area 0 R2(config-if)# interface loopback0 R2(config-if)# ipv6 ospf 100 area 0
Why this is correct
This is the correct configuration because it enables IPv6 routing, creates OSPFv3 process 100, and assigns unique router-IDs (1.1.1.1 and 2.2.2.2) that allow the routers to form a neighbor adjacency over the GigabitEthernet link. OSPFv3 is activated on both the GigabitEthernet0/0 interface and the loopback0 interface using the interface-specific 'ipv6 ospf 100 area 0' command, which is the proper configuration method for OSPFv3. Because the loopback interfaces are enabled in OSPF, their IPv6 prefixes are advertised, making the loopback networks reachable from the opposite router.
- ✗
R1(config)# ipv6 unicast-routing R1(config)# ipv6 router ospf 100 R1(config-rtr)# router-id 1.1.1.1 R1(config-rtr)# network 2001:db8:12::0/64 area 0 R1(config-rtr)# network 2001:db8:1::0/64 area 0 R2(config)# ipv6 unicast-routing R2(config)# ipv6 router ospf 100 R2(config-rtr)# router-id 2.2.2.2 R2(config-rtr)# network 2001:db8:12::0/64 area 0 R2(config-rtr)# network 2001:db8:2::0/64 area 0
Why it's wrong here
This configuration is incorrect because OSPFv3 on Cisco IOS does not use the IPv4-style 'network' command under router configuration mode; that command is only valid for OSPFv2. In OSPFv3, interfaces must be placed into the OSPF process individually using the interface-level 'ipv6 ospf 100 area 0' command. Since no interface is enabled for OSPFv3, the routers will not send or process OSPFv3 hello packets, and no adjacency or route exchange can occur.
- ✗
R1(config)# ipv6 unicast-routing R1(config)# ipv6 router ospf 100 R1(config-rtr)# router-id 1.1.1.1 R1(config-rtr)# interface gigabitethernet0/0 R1(config-if)# ipv6 ospf 100 area 0 R2(config)# ipv6 unicast-routing R2(config)# ipv6 router ospf 100 R2(config-rtr)# router-id 2.2.2.2 R2(config-rtr)# interface gigabitethernet0/0 R2(config-if)# ipv6 ospf 100 area 0
Why it's wrong here
This configuration is wrong because OSPFv3 is enabled only on the GigabitEthernet0/0 interfaces; the loopback0 interfaces are left out of the OSPFv3 process. Without the 'ipv6 ospf 100 area 0' command under loopback0, the loopback IPv6 prefixes are not advertised into OSPF, so R1 and R2 will not install each other's loopback routes in their routing tables. The GigabitEthernet link will form an adjacency, but the loopback networks will remain unreachable, failing the requirement.
- ✗
R1(config)# ipv6 unicast-routing R1(config)# ipv6 router ospf 100 R1(config-rtr)# router-id 1.1.1.1 R1(config-rtr)# interface gigabitethernet0/0 R1(config-if)# ipv6 ospf 100 area 0 R1(config-if)# interface loopback0 R1(config-if)# ipv6 ospf 100 area 0 R2(config)# ipv6 unicast-routing R2(config)# ipv6 router ospf 100 R2(config-rtr)# router-id 1.1.1.1 R2(config-rtr)# interface gigabitethernet0/0 R2(config-if)# ipv6 ospf 100 area 0 R2(config-if)# interface loopback0 R2(config-if)# ipv6 ospf 100 area 0
Why it's wrong here
Both routers have been configured with the identical router-ID 1.1.1.1, which is invalid for OSPFv3 because router-IDs must be unique throughout the OSPF routing domain. When a router receives a hello packet advertising the same router-ID it uses itself, it rejects the neighbor and will not form an adjacency. Consequently, no OSPF database synchronization occurs, and neither router learns the other's loopback or link prefixes, so traffic between the routers fails.
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.
✓R1(config)# ipv6 unicast-routing R1(config)# ipv6 router ospf 100 R1(config-rtr)# router-id 1.1.1.1 R1(config-rtr)# interface gigabitethernet0/0 R1(config-if)# ipv6 ospf 100 area 0 R1(config-if)# interface loopback0 R1(config-if)# ipv6 ospf 100 area 0 R2(config)# ipv6 unicast-routing R2(config)# ipv6 router ospf 100 R2(config-rtr)# router-id 2.2.2.2 R2(config-rtr)# interface gigabitethernet0/0 R2(config-if)# ipv6 ospf 100 area 0 R2(config-if)# interface loopback0 R2(config-if)# ipv6 ospf 100 area 0Correct answer▾
Why this is correct
This is the correct configuration because it enables IPv6 routing, creates OSPFv3 process 100, and assigns unique router-IDs (1.1.1.1 and 2.2.2.2) that allow the routers to form a neighbor adjacency over the GigabitEthernet link. OSPFv3 is activated on both the GigabitEthernet0/0 interface and the loopback0 interface using the interface-specific 'ipv6 ospf 100 area 0' command, which is the proper configuration method for OSPFv3. Because the loopback interfaces are enabled in OSPF, their IPv6 prefixes are advertised, making the loopback networks reachable from the opposite router.
✗R1(config)# ipv6 unicast-routing R1(config)# ipv6 router ospf 100 R1(config-rtr)# router-id 1.1.1.1 R1(config-rtr)# network 2001:db8:12::0/64 area 0 R1(config-rtr)# network 2001:db8:1::0/64 area 0 R2(config)# ipv6 unicast-routing R2(config)# ipv6 router ospf 100 R2(config-rtr)# router-id 2.2.2.2 R2(config-rtr)# network 2001:db8:12::0/64 area 0 R2(config-rtr)# network 2001:db8:2::0/64 area 0Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that OSPFv3 uses interface-level configuration, not network statements like OSPFv2 for IPv4.
Why candidates choose this
Candidates familiar with OSPFv2 for IPv4 might mistakenly apply the same 'network' command syntax to OSPFv3.
✗R1(config)# ipv6 unicast-routing R1(config)# ipv6 router ospf 100 R1(config-rtr)# router-id 1.1.1.1 R1(config-rtr)# interface gigabitethernet0/0 R1(config-if)# ipv6 ospf 100 area 0 R2(config)# ipv6 unicast-routing R2(config)# ipv6 router ospf 100 R2(config-rtr)# router-id 2.2.2.2 R2(config-rtr)# interface gigabitethernet0/0 R2(config-if)# ipv6 ospf 100 area 0Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that OSPFv3 must be enabled on all interfaces that should participate in the routing process, including loopback interfaces.
Why candidates choose this
Candidates might think that only the transit link needs OSPFv3, forgetting that loopback networks must also be advertised to be reachable.
✗R1(config)# ipv6 unicast-routing R1(config)# ipv6 router ospf 100 R1(config-rtr)# router-id 1.1.1.1 R1(config-rtr)# interface gigabitethernet0/0 R1(config-if)# ipv6 ospf 100 area 0 R1(config-if)# interface loopback0 R1(config-if)# ipv6 ospf 100 area 0 R2(config)# ipv6 unicast-routing R2(config)# ipv6 router ospf 100 R2(config-rtr)# router-id 1.1.1.1 R2(config-rtr)# interface gigabitethernet0/0 R2(config-if)# ipv6 ospf 100 area 0 R2(config-if)# interface loopback0 R2(config-if)# ipv6 ospf 100 area 0Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that OSPF router-ids must be unique. Using the same router-id on both routers prevents proper neighbor formation.
Why candidates choose this
Candidates might overlook the need for unique router-ids, especially if they are focused on other configuration details.
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?”
Visual reference
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
Area 0
Area 0 is the backbone area in OSPF routing that connects all other OSPF areas to ensure a loop-free and efficient network routing topology.
Key term
OSPF
OSPF is a link-state routing protocol used to find the best path for data packets to travel across IP networks, like a smart GPS that recalculates routes when traffic changes.
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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.