The correct answer is to configure OSPFv3 on both routers using interface-level commands, specifically enabling OSPFv3 process 100 in area 0 on R1’s G0/0, R2’s G0/0, and R2’s loopback0, with a router-id assigned under the `ipv6 router ospf 100` process. This works because OSPFv3 for IPv6 does not use the traditional `network` statement; instead, it relies on per-interface activation via `ipv6 ospf <process-id> area <area-id>`, and the loopback must be explicitly included to advertise its prefix into the OSPF domain. On the CCNA 200-301 v2 exam, this question tests your ability to distinguish OSPFv3 configuration from OSPFv2, with a common trap being the mistaken use of the `network` command or forgetting to enable OSPF on the loopback interface. A key memory tip is: "OSPFv3 is interface-driven, not network-driven—if you want a route, enable it on that interface."
CCNA IP Routing Practice Question
This 200-301 practice question tests your understanding of ip routing. 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.
You are connected to R1 via console. Configure OSPFv3 for IPv6 on both R1 and R2 so that the loopback0 interface on R2 (IPv6 address 2001:db8:1:2::1/64) is reachable from R1. The link between R1 and R2 uses the subnet 2001:db8:1:1::/64 with R1's G0/0 having IPv6 address 2001:db8:1:1::1/64 and R2's G0/0 having 2001:db8:1:1::2/64. OSPFv3 process ID must be 100 and all interfaces must be in area 0. After configuration, verify OSPFv3 neighbors and the IPv6 route to the loopback0 network.
On R1: ipv6 router ospf 100, router-id 1.1.1.1, interface g0/0: ipv6 ospf 100 area 0. On R2: ipv6 router ospf 100, router-id 2.2.2.2, interface g0/0: ipv6 ospf 100 area 0, interface loopback0: ipv6 ospf 100 area 0.
This configuration correctly enables OSPFv3 process 100 on both routers, assigns unique router IDs, and enables OSPFv3 on the required interfaces in area 0. Including loopback0 on R2 ensures the loopback network is advertised to R1.
B
On R1: ipv6 router ospf 100, router-id 1.1.1.1, interface g0/0: ipv6 ospf 100 area 0. On R2: ipv6 router ospf 100, router-id 2.2.2.2, interface g0/0: ipv6 ospf 100 area 0. No configuration on loopback0.
Why wrong: This is incorrect because the loopback0 interface on R2 is not included in OSPFv3, so its route will not be advertised to R1. The loopback network must be explicitly enabled under OSPFv3.
C
On R1: ipv6 router ospf 100, router-id 1.1.1.1, interface g0/0: ipv6 ospf 100 area 0. On R2: ipv6 router ospf 100, router-id 2.2.2.2, interface g0/0: ipv6 ospf 100 area 0, interface loopback0: ipv6 ospf 100 area 0, and also configure 'network 2001:db8:1:2::/64 area 0' under the OSPFv3 process.
Why wrong: This is incorrect because OSPFv3 does not use the 'network' command under the router process; that is an OSPFv2 (IPv4) feature. OSPFv3 enables interfaces directly under the interface configuration.
D
On R1: ipv6 router ospf 100, router-id 1.1.1.1, interface g0/0: ipv6 ospf 100 area 0. On R2: ipv6 router ospf 100, router-id 2.2.2.2, interface g0/0: ipv6 ospf 100 area 0, interface loopback0: ipv6 ospf 100 area 0, and also configure 'passive-interface GigabitEthernet0/0' under the OSPFv3 process.
Why wrong: This is incorrect because while the loopback0 is included, making it a passive interface is unnecessary and does not affect route advertisement. However, the configuration is still valid but not required; the question asks for the minimal correct configuration. More importantly, the passive-interface command is not needed and might be considered extraneous, but the core error is that the configuration is not minimal. However, the question expects the exact correct steps without extra commands. The passive-interface command is not wrong per se, but it is not required and could be seen as incorrect if the question expects only necessary commands. However, the main issue is that the configuration is still correct, but the option includes an unnecessary command. To maintain strict correctness, this option is considered incorrect because it adds an unnecessary command that is not part of the standard configuration for this scenario.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
On R1: ipv6 router ospf 100, router-id 1.1.1.1, interface g0/0: ipv6 ospf 100 area 0. On R2: ipv6 router ospf 100, router-id 2.2.2.2, interface g0/0: ipv6 ospf 100 area 0, interface loopback0: ipv6 ospf 100 area 0.
To achieve reachability to R2's loopback, OSPFv3 must be enabled on R1's and R2's G0/0 interfaces in area 0, and on R2's loopback0 so its prefix is advertised. Option A shows the minimal correct configuration. Option B omits enabling OSPF on loopback0, so the route to 2001:db8:1:2::/64 is not advertised. Option C incorrectly uses the 'network' command, which is not supported in OSPFv3; OSPFv3 relies on interface-level 'ipv6 ospf ... area' commands. Option D adds 'passive-interface GigabitEthernet0/0', which prevents OSPF from forming a neighbor adjacency on the link, breaking the required connectivity.
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.
✓
On R1: ipv6 router ospf 100, router-id 1.1.1.1, interface g0/0: ipv6 ospf 100 area 0. On R2: ipv6 router ospf 100, router-id 2.2.2.2, interface g0/0: ipv6 ospf 100 area 0, interface loopback0: ipv6 ospf 100 area 0.
Why this is correct
This configuration correctly enables OSPFv3 process 100 on both routers, assigns unique router IDs, and enables OSPFv3 on the required interfaces in area 0. Including loopback0 on R2 ensures the loopback network is advertised to R1.
On R1: ipv6 router ospf 100, router-id 1.1.1.1, interface g0/0: ipv6 ospf 100 area 0. On R2: ipv6 router ospf 100, router-id 2.2.2.2, interface g0/0: ipv6 ospf 100 area 0. No configuration on loopback0.
Why it's wrong here
This is incorrect because the loopback0 interface on R2 is not included in OSPFv3, so its route will not be advertised to R1. The loopback network must be explicitly enabled under OSPFv3.
✗
On R1: ipv6 router ospf 100, router-id 1.1.1.1, interface g0/0: ipv6 ospf 100 area 0. On R2: ipv6 router ospf 100, router-id 2.2.2.2, interface g0/0: ipv6 ospf 100 area 0, interface loopback0: ipv6 ospf 100 area 0, and also configure 'network 2001:db8:1:2::/64 area 0' under the OSPFv3 process.
Why it's wrong here
This is incorrect because OSPFv3 does not use the 'network' command under the router process; that is an OSPFv2 (IPv4) feature. OSPFv3 enables interfaces directly under the interface configuration.
✗
On R1: ipv6 router ospf 100, router-id 1.1.1.1, interface g0/0: ipv6 ospf 100 area 0. On R2: ipv6 router ospf 100, router-id 2.2.2.2, interface g0/0: ipv6 ospf 100 area 0, interface loopback0: ipv6 ospf 100 area 0, and also configure 'passive-interface GigabitEthernet0/0' under the OSPFv3 process.
Why it's wrong here
This is incorrect because while the loopback0 is included, making it a passive interface is unnecessary and does not affect route advertisement. However, the configuration is still valid but not required; the question asks for the minimal correct configuration. More importantly, the passive-interface command is not needed and might be considered extraneous, but the core error is that the configuration is not minimal. However, the question expects the exact correct steps without extra commands. The passive-interface command is not wrong per se, but it is not required and could be seen as incorrect if the question expects only necessary commands. However, the main issue is that the configuration is still correct, but the option includes an unnecessary command. To maintain strict correctness, this option is considered incorrect because it adds an unnecessary command that is not part of the standard configuration for this scenario.
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.
✓On R1: ipv6 router ospf 100, router-id 1.1.1.1, interface g0/0: ipv6 ospf 100 area 0. On R2: ipv6 router ospf 100, router-id 2.2.2.2, interface g0/0: ipv6 ospf 100 area 0, interface loopback0: ipv6 ospf 100 area 0.Correct answer▾
Why this is correct
This configuration correctly enables OSPFv3 process 100 on both routers, assigns unique router IDs, and enables OSPFv3 on the required interfaces in area 0. Including loopback0 on R2 ensures the loopback network is advertised to R1.
✗On R1: ipv6 router ospf 100, router-id 1.1.1.1, interface g0/0: ipv6 ospf 100 area 0. On R2: ipv6 router ospf 100, router-id 2.2.2.2, interface g0/0: ipv6 ospf 100 area 0. No configuration on loopback0.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that loopback0 is not configured with 'ipv6 ospf 100 area 0', so its prefix is not advertised.
Why candidates choose this
Candidates might think loopback interfaces are automatically advertised, but OSPFv3 requires explicit interface-level configuration.
✗On R1: ipv6 router ospf 100, router-id 1.1.1.1, interface g0/0: ipv6 ospf 100 area 0. On R2: ipv6 router ospf 100, router-id 2.2.2.2, interface g0/0: ipv6 ospf 100 area 0, interface loopback0: ipv6 ospf 100 area 0, and also configure 'network 2001:db8:1:2::/64 area 0' under the OSPFv3 process.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is using the 'network' command in OSPFv3, which is invalid. OSPFv3 uses interface-level configuration only.
Why candidates choose this
Candidates familiar with OSPFv2 might mistakenly apply the 'network' command to OSPFv3, not realizing the difference.
✗On R1: ipv6 router ospf 100, router-id 1.1.1.1, interface g0/0: ipv6 ospf 100 area 0. On R2: ipv6 router ospf 100, router-id 2.2.2.2, interface g0/0: ipv6 ospf 100 area 0, interface loopback0: ipv6 ospf 100 area 0, and also configure 'passive-interface GigabitEthernet0/0' under the OSPFv3 process.Wrong answer — click to see why▾
Why this is wrong here
Using 'passive-interface' on the transit link GigabitEthernet0/0 prevents OSPF from forming an adjacency, so neighbor verification would fail.
Why candidates choose this
Candidates might think that loopback interfaces should be made passive to prevent OSPF hello packets, but this is unnecessary and not part of the required 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.
Trap categories for this question
Command / output trap
This is incorrect because OSPFv3 does not use the 'network' command under the router process; that is an OSPFv2 (IPv4) feature. OSPFv3 enables interfaces directly under the interface configuration.
Scenario analysis trap
This is incorrect because while the loopback0 is included, making it a passive interface is unnecessary and does not affect route advertisement. However, the configuration is still valid but not required; the question asks for the minimal correct configuration. More importantly, the passive-interface command is not needed and might be considered extraneous, but the core error is that the configuration is not minimal. However, the question expects the exact correct steps without extra commands. The passive-interface command is not wrong per se, but it is not required and could be seen as incorrect if the question expects only necessary commands. However, the main issue is that the configuration is still correct, but the option includes an unnecessary command. To maintain strict correctness, this option is considered incorrect because it adds an unnecessary command that is not part of the standard configuration for this scenario.
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: On R1: ipv6 router ospf 100, router-id 1.1.1.1, interface g0/0: ipv6 ospf 100 area 0. On R2: ipv6 router ospf 100, router-id 2.2.2.2, interface g0/0: ipv6 ospf 100 area 0, interface loopback0: ipv6 ospf 100 area 0. — To achieve reachability to R2's loopback, OSPFv3 must be enabled on R1's and R2's G0/0 interfaces in area 0, and on R2's loopback0 so its prefix is advertised. Option A shows the minimal correct configuration. Option B omits enabling OSPF on loopback0, so the route to 2001:db8:1:2::/64 is not advertised. Option C incorrectly uses the 'network' command, which is not supported in OSPFv3; OSPFv3 relies on interface-level 'ipv6 ospf ... area' commands. Option D adds 'passive-interface GigabitEthernet0/0', which prevents OSPF from forming a neighbor adjacency on the link, breaking the required connectivity.
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. You are connected to R1. The network must route IPv6 traffic between two directly connected routers using OSPFv3. Configure OSPFv3 on R1's GigabitEthernet0/0 interface in area 0, enable IPv6 unicast routing, and verify that R1 forms an OSPFv3 neighbor adjacency with R2 and learns the remote network 2001:DB8:CAFE:2::/64 via OSPFv3.
hard
✓ A.Enable OSPFv3 on the interface with 'ipv6 ospf 1 area 0' under GigabitEthernet0/0.
B.Configure 'ipv6 router ospf 1' and then 'network 2001:DB8:CAFE:1::/64 area 0' under the OSPFv3 process.
C.Enable OSPFv3 on the interface with 'ipv6 ospf 1 area 0' under the OSPFv3 router configuration mode.
D.Configure 'ipv6 unicast-routing' and then 'ipv6 ospf 1 area 0' under the interface.
Why A: The issue is that OSPFv3 is not enabled on R1's GigabitEthernet0/0 interface, and the OSPFv3 routing process has not been started. To fix this, first ensure ipv6 unicast-routing is already enabled (it is). Then configure the OSPFv3 process with a process ID (e.g., 1) and enable OSPFv3 on the interface in area 0 using the command 'ipv6 ospf 1 area 0' under the interface. After that, R1 will form a neighbor adjacency with R2 and learn the remote route.
Last reviewed: Jun 6, 2026
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