- A
It prevents OSPF from sending hello packets on that interface.
This is correct because passive interfaces suppress OSPF hello exchange locally.
- B
It can still allow the connected network to be advertised into OSPF.
This is correct because the network can still be advertised through other active OSPF relationships.
- C
It changes OSPF into a static route on that interface.
Why wrong: This is wrong because passive-interface does not convert OSPF into static routing.
- D
It forces the interface to become the router ID.
Why wrong: This is wrong because passive-interface does not determine the router ID.
- E
It disables OSPF on every interface in the router automatically.
Why wrong: This is wrong because passive-interface affects only the specified interface unless broader defaults are configured.
Quick Answer
The correct answer is that an OSPF passive interface stops hello packet exchange while still allowing the connected network to be advertised into OSPF. This works because the passive command suppresses the formation of neighbor adjacencies on that interface, preventing the router from sending or listening for Hello packets, yet the network itself remains part of the OSPF link-state database and is advertised via other active interfaces. On the CCNA 200-301 v2 exam, this concept tests your understanding of OSPF neighbor behavior versus network advertisement, often appearing as a two-part multiple-choice question where the wrong answers claim passive disables OSPF entirely or removes the subnet from routing. A common trap is confusing passive with “shutdown” or “network under router ospf” removal. Memory tip: think of a passive interface as a “silent member” of OSPF—it listens to no one, but the network still gets a seat at the table.
CCNA IP Routing Practice Question
This 200-301 practice question tests your understanding of ip routing. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: an OSPF passive interface prevents the router from sending OSPF hello packets on that interface, stopping neighbor adjacency formation.. 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.
Which two statements accurately describe OSPF passive interfaces?
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
It prevents OSPF from sending hello packets on that interface.
An OSPF passive interface stops hello packet exchange on that interface while still allowing the connected network to be advertised into OSPF through other active adjacencies. In plain language, it tells the router not to try to form neighbors on that interface, but not to forget that the network exists. This is very useful on user-facing or stub-like interfaces where no routing neighbor should appear. The wrong answers often treat passive as if it disables OSPF globally or removes the network completely. The two correct answers are the ones that preserve the suppression of adjacency on that interface and the continued advertisement of the connected network.
Key principle: An OSPF passive interface prevents the router from sending OSPF hello packets on that interface, stopping neighbor adjacency formation.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
It prevents OSPF from sending hello packets on that interface.
- ✓
It can still allow the connected network to be advertised into OSPF.
- ✗
It changes OSPF into a static route on that interface.
Why it's wrong here
This is wrong because passive-interface does not convert OSPF into static routing.
When this WOULD be correct
In a different question asking about the effects of configuring OSPF on a specific interface, if the question stated that passive interfaces behave like static routes in terms of not participating in OSPF neighbor relationships, option C could be considered correct.
- ✗
It forces the interface to become the router ID.
Why it's wrong here
This is wrong because passive-interface does not determine the router ID.
- ✗
It disables OSPF on every interface in the router automatically.
Why it's wrong here
This is wrong because passive-interface affects only the specified interface unless broader defaults are configured.
When this WOULD be correct
In a different question, if it asked about a command that globally disables OSPF on all interfaces when applied, then 'disables OSPF on every interface in the router automatically' could be correct in the context of a command that applies to all interfaces, such as 'router ospf 1' with a specific configuration.
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.
✓It prevents OSPF from sending hello packets on that interface.Correct answer▾
Why this is correct
This is correct because passive interfaces suppress OSPF hello exchange locally.
✗It changes OSPF into a static route on that interface.Wrong answer — click to see why▾
Why this is wrong here
The passive-interface command does not convert OSPF to static routing. OSPF remains a dynamic routing protocol; the interface simply stops sending and receiving OSPF hello packets. The network is still advertised via OSPF if configured appropriately.
★ When this WOULD be the correct answer
In a different question asking about the effects of configuring OSPF on a specific interface, if the question stated that passive interfaces behave like static routes in terms of not participating in OSPF neighbor relationships, option C could be considered correct.
Why candidates choose this
The term 'passive' might be misinterpreted as making the route static or non-dynamic. Students may think that a passive interface means the route becomes static, but in OSPF, passive only suppresses hello packets, not the dynamic advertisement of the network.
✗It forces the interface to become the router ID.Wrong answer — click to see why▾
Why this is wrong here
The passive-interface command does not influence the router ID selection. The router ID is determined by the highest loopback IP address, then the highest physical IP address, or manually configured with the router-id command. Passive-interface only affects OSPF operation on that interface.
★ When this WOULD be the correct answer
In a question asking about OSPF configuration where the context is about defining router roles or attributes, one might state that a specific interface is being used to define the router ID, making it the correct answer in that scenario.
Why candidates choose this
Students might confuse the passive-interface command with other OSPF configuration commands that affect router identity, such as router-id, or mistakenly think that making an interface passive somehow promotes it to a special role like the router ID.
✗It disables OSPF on every interface in the router automatically.Wrong answer — click to see why▾
Why this is wrong here
By default, the passive-interface command applies only to the specified interface. To make all interfaces passive by default, the passive-interface default command must be used, followed by no passive-interface on specific interfaces where adjacencies are desired.
★ When this WOULD be the correct answer
In a different question, if it asked about a command that globally disables OSPF on all interfaces when applied, then 'disables OSPF on every interface in the router automatically' could be correct in the context of a command that applies to all interfaces, such as 'router ospf 1' with a specific configuration.
Why candidates choose this
The word 'passive' might imply a global effect, and students may assume that configuring passive-interface on one interface disables OSPF on all interfaces. However, OSPF passive interfaces are interface-specific unless the default keyword is used.
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 common exam trap is to confuse the effect of the OSPF passive interface command with disabling OSPF entirely on that interface or converting OSPF routes into static routes. Some candidates mistakenly believe that passive interfaces stop all OSPF activity or remove the network from OSPF advertisements. In reality, passive interfaces only stop OSPF hello packets and adjacency formation but continue to advertise the connected network. Misunderstanding this can lead to incorrect answers or network misconfigurations, especially when interpreting how OSPF maintains routing information despite passive interfaces.
Detailed technical explanation
How to think about this question
OSPF passive interfaces are a key feature in OSPF routing that allow network administrators to control OSPF neighbor formation on specific interfaces. When an interface is configured as passive, the router stops sending OSPF hello packets on that interface, preventing the establishment of OSPF adjacencies. However, the router continues to advertise the network connected to that interface in OSPF LSAs (Link-State Advertisements), ensuring that the network remains reachable within the OSPF domain. This behavior is particularly useful for interfaces connected to end hosts or stub networks where no OSPF neighbors should form. The decision to configure an interface as passive is based on the need to suppress OSPF neighbor discovery without removing the network from OSPF routing updates. This means that while OSPF adjacency formation is disabled on the passive interface, the network itself is still included in the OSPF routing process. Cisco routers implement this by stopping hello packet transmission on the passive interface but still advertising the connected subnet in OSPF LSDB (Link-State Database). This helps reduce unnecessary OSPF traffic and improves security by limiting OSPF neighbor relationships to only intended interfaces. A common exam trap is to assume that configuring an interface as passive disables OSPF entirely on that interface or converts OSPF routes into static routes. Neither is true. Passive interfaces only prevent OSPF hello packets and adjacency formation but do not disable OSPF routing or network advertisement. Understanding this distinction is critical for CCNA candidates, as misinterpreting passive interface behavior can lead to incorrect network design or exam answers. Practically, passive interfaces are widely used on user-facing ports or links to stub networks to optimize OSPF operation and security.
KKey Concepts to Remember
- An OSPF passive interface prevents the router from sending OSPF hello packets on that interface, stopping neighbor adjacency formation.
- OSPF passive interfaces still allow the connected network to be advertised in OSPF LSAs, maintaining routing reachability.
- Configuring an interface as passive does not disable OSPF routing globally or on other interfaces of the router.
- Passive interfaces are typically used on interfaces connected to end devices or stub networks where no OSPF neighbors should form.
- OSPF hello packets are essential for neighbor discovery, and suppressing them on passive interfaces prevents adjacency establishment.
- The passive-interface command in Cisco IOS affects only the specified interface unless applied globally to all interfaces.
- OSPF passive interfaces do not convert OSPF routes into static routes or affect the router ID selection process.
- Using passive interfaces improves network security and reduces unnecessary OSPF traffic on interfaces without neighbors.
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
An OSPF passive interface prevents the router from sending OSPF hello packets on that interface, stopping neighbor adjacency formation.
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.
What to study next
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FAQ
Questions learners often ask
What does this 200-301 question test?
IP Routing — This question tests IP Routing — An OSPF passive interface prevents the router from sending OSPF hello packets on that interface, stopping neighbor adjacency formation..
What is the correct answer to this question?
The correct answer is: It prevents OSPF from sending hello packets on that interface. — An OSPF passive interface stops hello packet exchange on that interface while still allowing the connected network to be advertised into OSPF through other active adjacencies. In plain language, it tells the router not to try to form neighbors on that interface, but not to forget that the network exists. This is very useful on user-facing or stub-like interfaces where no routing neighbor should appear. The wrong answers often treat passive as if it disables OSPF globally or removes the network completely. The two correct answers are the ones that preserve the suppression of adjacency on that interface and the continued advertisement of the connected network.
What should I do if I get this 200-301 question wrong?
Review an OSPF passive interface prevents the router from sending OSPF hello packets on that interface, stopping neighbor adjacency formation., then practise related 200-301 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
An OSPF passive interface prevents the router from sending OSPF hello packets on that interface, stopping neighbor adjacency formation.
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Same concept, more angles
1 more ways this is tested on 200-301
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. Which two statements accurately describe passive interfaces in OSPF?
medium- ✓ A.It suppresses OSPF hello packets on that interface.
- ✓ B.It can still allow the connected network to be advertised into OSPF.
- C.It converts OSPF on that interface into static routing.
- D.It forces the interface IP address to become the router ID.
- E.It disables OSPF on every interface in the router automatically.
Why A: A passive interface stops the router from sending OSPF hello packets on that interface, which means the router will not try to form neighbors there. In practical terms, this is useful on user-facing or stub-like links where no OSPF neighbor should exist. However, passive does not necessarily mean the connected network disappears from OSPF. The network can still be advertised through the router’s other active adjacencies. This is a common design and security practice because it reduces unnecessary routing chatter on interfaces that should not form adjacencies in the first place.
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Last reviewed: Apr 12, 2026
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