The answer is to enable IPv6 unicast routing globally, create the OSPFv3 process with a router-id, and then activate OSPFv3 directly on each interface using the `ipv6 ospf 100 area 0` command. This is correct because OSPFv3 operates per-interface rather than under a network statement like OSPFv2, and IPv6 routing must be explicitly enabled for the router to forward IPv6 traffic. On the CCNA 200-301 v2 exam, this task tests your ability to configure OSPFv3 for IPv6 without the common trap of forgetting the `ipv6 unicast-routing` command or the mandatory router-id, which OSPFv3 requires even if no IPv4 addresses are configured. A key memory tip is “OSPFv3 is interface-driven, not network-driven”—you enable it on the link, not by matching a prefix. For quick recall, remember the three-step sequence: unicast-routing, router ospf with a router-id, then interface-level activation.
CCNA IP Routing Practice Question
This 200-301 practice question tests your understanding of ip routing. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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. 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.
This configuration correctly enables IPv6 routing, creates OSPFv3 process 100 with a unique router-id, and enables OSPFv3 on both interfaces in area 0. This allows the loopback networks to be advertised and reachable.
Why wrong: This is incorrect because OSPFv3 does not use the 'network' command under the router configuration mode. OSPFv3 uses interface-level configuration with the 'ipv6 ospf' command.
Why wrong: This is incorrect because the loopback0 interfaces are not enabled for OSPFv3. Without enabling OSPFv3 on the loopback interfaces, their networks are not advertised, so R1 and R2 cannot learn each other's loopback routes.
Why wrong: This is incorrect because both routers use the same router-id 1.1.1.1. OSPF requires unique router-ids within the same routing domain; duplicate router-ids can cause adjacency issues.
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.
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.
This configuration correctly enables IPv6 routing, creates OSPFv3 process 100 with a unique router-id, and enables OSPFv3 on both interfaces in area 0. This allows the loopback networks to be advertised and reachable.
This is incorrect because OSPFv3 does not use the 'network' command under the router configuration mode. OSPFv3 uses interface-level configuration with the 'ipv6 ospf' command.
This is incorrect because the loopback0 interfaces are not enabled for OSPFv3. Without enabling OSPFv3 on the loopback interfaces, their networks are not advertised, so R1 and R2 cannot learn each other's loopback routes.
This is incorrect because both routers use the same router-id 1.1.1.1. OSPF requires unique router-ids within the same routing domain; duplicate router-ids can cause adjacency issues.
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.
This configuration correctly enables IPv6 routing, creates OSPFv3 process 100 with a unique router-id, and enables OSPFv3 on both interfaces in area 0. This allows the loopback networks to be advertised and reachable.
✗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.
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.
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?”
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.
Trap categories for this question
Command / output trap
This is incorrect because OSPFv3 does not use the 'network' command under the router configuration mode. OSPFv3 uses interface-level configuration with the 'ipv6 ospf' command.
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: 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.
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
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Drag and drop the following steps into the correct order to configure OSPFv3 for IPv6 on a Cisco IOS-XE router.
medium
✓ A.Enable IPv6 routing globally with 'ipv6 unicast-routing'
✓ B.Enter OSPFv3 configuration mode with 'router ospfv3 1'
✓ C.Configure OSPFv3 on each interface with 'ipv6 ospf <process-id> area <area-id>'
✓ D.Verify OSPFv3 adjacency with 'show ipv6 ospf neighbor'
Why A: To configure OSPFv3 for IPv6, first enable IPv6 routing globally with 'ipv6 unicast-routing'. Next, enter OSPFv3 configuration mode using 'router ospfv3 1' to set process parameters. Then, apply OSPFv3 on each interface with 'ipv6 ospf <process-id> area <area-id>'. Finally, verify adjacencies with 'show ipv6 ospf neighbor'.
Variation 2. Drag and drop the following steps into the correct order to configure OSPFv3 for IPv6 on a Cisco router and verify basic neighbor relationships.
medium
✓ A.Enable IPv6 routing globally with the 'ipv6 unicast-routing' command.
✓ B.Create the OSPFv3 routing process using the 'ipv6 router ospf 1' command.
✓ C.Enter interface configuration mode for the interface that will participate in OSPFv3.
✓ D.Enable IPv6 on the interface using the 'ipv6 enable' command, which automatically generates a link-local address.
✓ E.Assign the interface to OSPFv3 area 0 using the 'ipv6 ospf 1 area 0' command.
✓ F.Verify OSPFv3 neighbor adjacencies with the 'show ospfv3 neighbor' command.
Why A: IPv6 unicast routing must be enabled first, as OSPFv3 relies on the router being IPv6 aware. Next, the OSPFv3 process is created globally. The interface must then be IPv6-enabled to auto-generate the link-local address used by OSPFv3 for forming adjacencies. After that, the interface is added to OSPFv3 Area 0. Finally, the 'show ospfv3 neighbor' command is used to verify that an adjacency has formed.
Variation 3. Drag and drop the following steps into the correct order to configure and verify OSPFv3 neighbor adjacency using link-local addresses in area 0.
medium
✓ A.Enable IPv6 unicast routing with the 'ipv6 unicast-routing' global command.
✓ B.Create an OSPFv3 routing process using 'ipv6 router ospf 1'.
✓ C.Enter interface configuration mode with 'interface gigabitethernet0/0'.
✓ D.Assign the interface to OSPFv3 process 1 area 0 using 'ipv6 ospf 1 area 0'.
✓ E.Verify the adjacency by displaying OSPFv3 neighbors with 'show ipv6 ospf neighbor'.
Why A: The correct order enables IPv6 unicast routing globally, creates the OSPFv3 process, enters interface configuration, assigns the interface to the OSPFv3 process in area 0 (which activates OSPFv3 on the link), and finally verifies the neighbor relationship. IPv6 unicast routing must be enabled first because OSPFv3 requires IPv6 packet forwarding. The router process must exist before an interface can be associated with it. Assigning the interface to area 0 triggers Hello packet exchange over link-local addresses. The show command confirms the adjacency formed.
Last reviewed: Jun 6, 2026
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