- A
Configure the passive-interface Loopback0 command under the OSPF process.
The passive-interface command under the OSPF process prevents the interface from sending OSPF hello messages, but the network is still advertised in LSAs because OSPF includes the subnet in its database.
- B
Remove the network 192.168.12.0 0.0.0.3 area 0 command from the OSPF configuration.
Why wrong: This is incorrect because removing the network statement for the link between R1 and R2 would prevent OSPF from forming an adjacency on that interface, disrupting connectivity.
- C
Configure the ip ospf passive-interface command on GigabitEthernet0/0.
Why wrong: This is incorrect because the ip ospf passive-interface command is not a valid Cisco IOS command; the correct command is passive-interface under the OSPF process or ip ospf passive-interface under the interface (which is valid but not the standard approach). However, applying it to GigabitEthernet0/0 would suppress hellos on the transit link, preventing the OSPF adjacency with R2.
- D
Configure the network 192.168.12.0 0.0.0.3 area 0 command under the OSPF process.
Why wrong: This is incorrect because the network statement for the transit link is already assumed to be present; adding it again does not change behavior and does not suppress hello messages on Loopback0.
OSPF Passive Interface: Configuring Loopback Without Hello Messages
This 200-301 practice question tests your understanding of ip routing. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 the console. R1 and R2 are running OSPFv2 in area 0. R1's router ID is 1.1.1.1, and R2's router ID is 2.2.2.2. Both routers are connected via GigabitEthernet0/0 on the 192.168.12.0/30 subnet. You need to ensure that R1 does not send OSPF hello messages out of its Loopback0 interface, while still advertising the loopback network into OSPF.
Quick Answer
The answer is to configure the passive-interface Loopback0 command under the OSPF process. This is correct because setting a loopback as a passive interface suppresses the transmission of OSPF hello messages on that interface, preventing the router from forming any neighbor adjacency over it, while the network is still advertised into the OSPF domain via the router’s link-state advertisements. On the CCNA 200-301 v2 exam, this scenario tests your understanding that OSPF passive interfaces block hello packets but do not remove the subnet from the routing table or LSAs—a common trap is thinking that a passive interface stops the network from being advertised. Remember the key distinction: passive means “no hellos, but still advertised.” A useful memory tip is “Passive for peace, not for propagation”—the interface stays quiet but the route still speaks.
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
Configure the passive-interface Loopback0 command under the OSPF process.
Configuring the Loopback0 interface as passive under the OSPF process suppresses the sending of hello messages on that interface, preventing unnecessary adjacencies. The network is still advertised because OSPF includes the subnet in its LSAs.
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.
- ✓
Configure the passive-interface Loopback0 command under the OSPF process.
- ✗
Remove the network 192.168.12.0 0.0.0.3 area 0 command from the OSPF configuration.
Why it's wrong here
This is incorrect because removing the network statement for the link between R1 and R2 would prevent OSPF from forming an adjacency on that interface, disrupting connectivity.
- ✗
Configure the ip ospf passive-interface command on GigabitEthernet0/0.
Why it's wrong here
This is incorrect because the ip ospf passive-interface command is not a valid Cisco IOS command; the correct command is passive-interface under the OSPF process or ip ospf passive-interface under the interface (which is valid but not the standard approach). However, applying it to GigabitEthernet0/0 would suppress hellos on the transit link, preventing the OSPF adjacency with R2.
- ✗
Configure the network 192.168.12.0 0.0.0.3 area 0 command under the OSPF process.
Why it's wrong here
This is incorrect because the network statement for the transit link is already assumed to be present; adding it again does not change behavior and does not suppress hello messages on Loopback0.
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.
✓Configure the passive-interface Loopback0 command under the OSPF process.Correct answer▾
Why this is correct
The passive-interface command under the OSPF process prevents the interface from sending OSPF hello messages, but the network is still advertised in LSAs because OSPF includes the subnet in its database.
✗Remove the network 192.168.12.0 0.0.0.3 area 0 command from the OSPF configuration.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that the network statement for the transit link is necessary for OSPF adjacency; removing it would break the OSPF neighbor relationship.
Why candidates choose this
Candidates might think that removing the network statement from the transit link would stop hello messages on that interface, but it would actually prevent the adjacency entirely.
✗Configure the ip ospf passive-interface command on GigabitEthernet0/0.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that applying passive-interface to the transit link would prevent the OSPF neighbor relationship from forming, which is not the goal.
Why candidates choose this
Candidates might confuse the interface to be made passive, thinking that making the transit link passive would solve the problem, but it would break the adjacency.
✗Configure the network 192.168.12.0 0.0.0.3 area 0 command under the OSPF process.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that adding a network statement does not suppress hello messages; it only includes the interface in the OSPF process.
Why candidates choose this
Candidates might think that adding a network statement for the transit link would somehow affect hello suppression on Loopback0, but it is unrelated.
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 the ip ospf passive-interface command is not a valid Cisco IOS command; the correct command is passive-interface under the OSPF process or ip ospf passive-interface under the interface (which is valid but not the standard approach). However, applying it to GigabitEthernet0/0 would suppress hellos on the transit link, preventing the OSPF adjacency with R2.
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.
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.
What to study next
Got this wrong? Here's your next step.
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.
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FAQ
Questions learners often ask
What does this 200-301 question test?
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: Configure the passive-interface Loopback0 command under the OSPF process. — Configuring the Loopback0 interface as passive under the OSPF process suppresses the sending of hello messages on that interface, preventing unnecessary adjacencies. The network is still advertised because OSPF includes the subnet in its LSAs.
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.
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Last reviewed: Jun 7, 2026
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