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. A key principle to apply: oSPF passive interface configuration advertises the connected subnet without sending or receiving OSPF Hello packets on that interface.. 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.
A router advertises its LAN network into OSPF, but no OSPF Hellos should be sent toward end-user devices on that LAN. Which configuration approach solves this cleanly?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure the LAN interface as a passive interface in OSPF
A passive interface advertises the connected subnet into OSPF without sending or processing Hellos on that interface. That is exactly what you want for user-facing LANs with no OSPF neighbors.
Key principle: OSPF passive interface configuration advertises the connected subnet without sending or receiving OSPF Hello packets on that interface.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Use ip ospf cost 65535 on the LAN interface
Why it's wrong here
That changes the metric, not whether Hellos are sent.
When this WOULD be correct
In a scenario where the question asks for a method to influence OSPF path selection without needing to suppress Hello packets, setting the OSPF cost to 65535 could be correct. For example, if the question specifies that the goal is to manipulate OSPF metrics for routing decisions without affecting neighbor relationships.
✓
Configure the LAN interface as a passive interface in OSPF
Why this is correct
Passive interface stops Hellos while still advertising the subnet.
Related concept
OSPF passive interface configuration advertises the connected subnet without sending or receiving OSPF Hello packets on that interface.
✗
Disable OSPF globally and redistribute connected routes
Why it's wrong here
That is unnecessary and far messier.
When this WOULD be correct
If a question asked how to completely eliminate OSPF from a router while still allowing connected routes to be advertised through another routing protocol, then disabling OSPF globally would be the correct approach.
✗
Convert the LAN interface to a loopback
Why it's wrong here
That changes the interface type entirely and is not the normal fix.
When this WOULD be correct
If the question asked for a method to isolate OSPF routing from a specific segment of the network while still allowing the interface to function normally for other purposes, converting the LAN interface to a loopback could be a valid solution, as loopbacks are often used for management or routing purposes without direct user connectivity.
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 LAN interface as a passive interface in OSPFCorrect answer▾
Why this is correct
Passive interface stops Hellos while still advertising the subnet.
✗Use ip ospf cost 65535 on the LAN interfaceWrong answer — click to see why▾
Why this is wrong here
The 'ip ospf cost' command only modifies the OSPF metric for the interface, not the transmission of Hello packets. OSPF Hellos are still sent regardless of the cost value, so this does not prevent Hellos from reaching end-user devices.
★ When this WOULD be the correct answer
In a scenario where the question asks for a method to influence OSPF path selection without needing to suppress Hello packets, setting the OSPF cost to 65535 could be correct. For example, if the question specifies that the goal is to manipulate OSPF metrics for routing decisions without affecting neighbor relationships.
Why candidates choose this
Students might think that setting a very high cost could effectively suppress OSPF operations on the interface, but cost only affects route selection, not protocol behavior like Hello transmission.
✗Disable OSPF globally and redistribute connected routesWrong answer — click to see why▾
Why this is wrong here
Disabling OSPF globally and redistributing connected routes is an overly complex and messy approach. It removes OSPF entirely from the router, requiring redistribution of all connected routes, which can lead to suboptimal routing and administrative overhead. The passive-interface command achieves the goal cleanly without disabling OSPF.
★ When this WOULD be the correct answer
If a question asked how to completely eliminate OSPF from a router while still allowing connected routes to be advertised through another routing protocol, then disabling OSPF globally would be the correct approach.
Why candidates choose this
A test-taker might consider this option because redistribution can advertise routes without running OSPF on the interface, but they overlook that disabling OSPF globally affects all interfaces and requires additional configuration to re-advertise routes.
✗Convert the LAN interface to a loopbackWrong answer — click to see why▾
Why this is wrong here
Converting a LAN interface to a loopback interface changes its fundamental characteristics (e.g., it becomes a virtual interface that is always up) and is not a standard or clean solution for preventing OSPF Hellos. Loopback interfaces are typically used for router IDs or management, not for connecting end-user devices.
★ When this WOULD be the correct answer
If the question asked for a method to isolate OSPF routing from a specific segment of the network while still allowing the interface to function normally for other purposes, converting the LAN interface to a loopback could be a valid solution, as loopbacks are often used for management or routing purposes without direct user connectivity.
Why candidates choose this
Students might confuse the passive-interface concept with loopback interfaces, thinking that loopbacks do not send Hellos (which is true), but this approach is impractical and alters the network design unnecessarily.
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: answer the scenario, not the keyword
A frequent exam trap is selecting the option to increase the OSPF cost on the LAN interface to prevent Hello packets. While adjusting the cost changes the metric used for route selection, it does not stop the router from sending or receiving OSPF Hellos. Another common mistake is to disable OSPF globally and redistribute connected routes, which is unnecessarily complex and does not address the problem of suppressing Hellos on a specific interface. Additionally, converting the LAN interface to a loopback is irrelevant because loopbacks are logical interfaces used for router IDs and testing, not for controlling OSPF Hello behavior on physical LAN interfaces.
Detailed technical explanation
How to think about this question
OSPF (Open Shortest Path First) is a link-state routing protocol that uses Hello packets to discover and maintain neighbor relationships on interfaces. These Hello packets are multicast periodically to establish adjacencies and exchange routing information. However, on interfaces connected to end-user devices, such as LAN segments, forming OSPF neighbor adjacencies is unnecessary and can cause unwanted traffic and security concerns.
To address this, Cisco IOS provides the passive interface command within OSPF configuration. When an interface is set as passive, the router continues to advertise the connected subnet into the OSPF domain, ensuring that routing information is shared. However, it stops sending and receiving OSPF Hello packets on that interface, preventing neighbor formation. This approach is clean and efficient for LAN interfaces where no OSPF routers exist beyond the local segment.
A common exam trap is confusing passive interfaces with simply increasing the OSPF cost or redistributing connected routes globally. Changing the cost affects route selection but does not suppress Hello packets. Similarly, redistributing connected routes is a broader and more complex solution that does not selectively stop Hellos on a specific interface. Loopback interfaces serve different purposes and are not a valid solution for this scenario. Understanding the passive interface concept is critical for proper OSPF design and exam success.
KKey Concepts to Remember
OSPF passive interface configuration advertises the connected subnet without sending or receiving OSPF Hello packets on that interface.
OSPF Hello packets are essential for neighbor discovery and adjacency formation but are unnecessary on interfaces connected to end-user LANs.
Configuring an interface as passive in OSPF prevents unnecessary OSPF traffic toward devices that do not participate in OSPF routing.
OSPF cost changes on an interface affect route metric calculations but do not stop Hello packet transmission or neighbor formation.
Redistributing connected routes globally into OSPF is a complex approach that does not selectively suppress Hellos on specific interfaces.
Loopback interfaces are logical interfaces used for stable router IDs and testing, not for suppressing OSPF Hellos on LAN interfaces.
A passive interface in OSPF still advertises the subnet to other OSPF routers, ensuring routing information is propagated correctly.
Using passive interfaces improves network security and efficiency by reducing unnecessary OSPF traffic on user-facing LAN segments.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
OSPF passive interface configuration advertises the connected subnet without sending or receiving OSPF Hello packets on that interface.
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 passive interface configuration advertises the connected subnet without sending or receiving OSPF Hello packets on that interface., then practise related 200-301 questions on the same topic to reinforce the concept.
IP Routing — This question tests IP Routing — OSPF passive interface configuration advertises the connected subnet without sending or receiving OSPF Hello packets on that interface..
What is the correct answer to this question?
The correct answer is: Configure the LAN interface as a passive interface in OSPF — A passive interface advertises the connected subnet into OSPF without sending or processing Hellos on that interface. That is exactly what you want for user-facing LANs with no OSPF neighbors.
What should I do if I get this 200-301 question wrong?
Review oSPF passive interface configuration advertises the connected subnet without sending or receiving OSPF Hello packets on that interface., then practise related 200-301 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
OSPF passive interface configuration advertises the connected subnet without sending or receiving OSPF Hello packets on that interface.
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