The answer is that a passive interface in OSPF still advertises the connected network into the routing domain, even though it does not send Hello packets. This works because the router includes the passive interface’s subnet in its Link State Advertisements (LSAs), which are then flooded to neighbors formed on other active interfaces. The technical concept here is that OSPF separates the process of neighbor discovery from route advertisement; a passive interface simply disables the former while preserving the latter. On the CCNA 200-301 v2 exam, this distinction tests your understanding of OSPF operation on stub or user-facing links, where you want to announce the network without risking neighbor flapping. A common trap is assuming “passive” means the network is hidden entirely—it is not. Remember the memory tip: “Passive means no handshake, but the network still makes the guest list.”
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: a passive interface in OSPF prevents sending hello packets and forming neighbor adjacencies on that interface while still advertising the connected network.. 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.
Why does a passive interface in OSPF still matter even though it does not send hello packets?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The connected network can still be advertised into OSPF through other active adjacencies
A passive interface still matters because the connected network can still be advertised into OSPF even though the interface itself does not form neighbor relationships. In plain language, the router is saying, “This network is mine, and I want others to know about it, but I do not want to speak OSPF directly on this interface.” That is useful on user-facing or stub-like interfaces where no OSPF neighbor should exist.
This distinction is important because some engineers assume passive means “ignored entirely.” It does not. The connected network can still appear in routing updates sent through real neighbors on other interfaces. What changes is neighbor formation on the passive interface itself.
Key principle: A passive interface in OSPF prevents sending hello packets and forming neighbor adjacencies on that interface while still advertising the connected network.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
The connected network can still be advertised into OSPF through other active adjacencies
Why this is correct
This is correct because passive-interface suppresses hello exchange on that interface while still allowing the network to be advertised.
Related concept
A passive interface in OSPF prevents sending hello packets and forming neighbor adjacencies on that interface while still advertising the connected network.
✗
The passive interface automatically becomes the OSPF router ID
Why it's wrong here
This is wrong because passive-interface status does not determine the router ID.
When this WOULD be correct
In a different context, if a question asked about how OSPF selects a router ID and included a scenario where a passive interface was the only interface on the router, then this option could be correct as it would imply that the passive interface is the only available IP address for the router ID.
✗
The passive interface disables all OSPF operation on the router
Why it's wrong here
This is wrong because OSPF can still run and form adjacencies on other interfaces.
When this WOULD be correct
In a different exam question asking about the effects of configuring an interface as passive in OSPF, if the question stated that the passive interface would stop all OSPF processes on the router, then this option could be correct if the context was about a misconfigured router where all interfaces were set to passive.
✗
The passive interface converts OSPF into EIGRP on that link
Why it's wrong here
This is wrong because passive-interface affects OSPF hello behavior only.
When this WOULD be correct
In a different question, if it asked about a scenario where a routing protocol can be changed or configured to operate differently on a specific interface, one might mistakenly think that a command could convert OSPF to EIGRP, leading to this option being perceived as correct.
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.
✓The connected network can still be advertised into OSPF through other active adjacenciesCorrect answer▾
Why this is correct
This is correct because passive-interface suppresses hello exchange on that interface while still allowing the network to be advertised.
✗The passive interface automatically becomes the OSPF router IDWrong answer — click to see why▾
Why this is wrong here
The OSPF router ID is determined by the highest IP address on a loopback interface or the highest active physical interface IP at the time of OSPF process startup, not by passive-interface configuration. A passive interface does not influence router ID selection.
★ When this WOULD be the correct answer
In a different context, if a question asked about how OSPF selects a router ID and included a scenario where a passive interface was the only interface on the router, then this option could be correct as it would imply that the passive interface is the only available IP address for the router ID.
Why candidates choose this
Students might confuse the passive behavior (no hello packets) with the router ID election process, thinking that a passive interface, being 'inactive' in terms of hello exchange, could be used as a stable identifier. However, router ID is independent of hello suppression.
✗The passive interface disables all OSPF operation on the routerWrong answer — click to see why▾
Why this is wrong here
The passive-interface command only suppresses OSPF hello packets on that specific interface; OSPF continues to operate normally on other interfaces, forming adjacencies and exchanging routing information. It does not disable OSPF globally.
★ When this WOULD be the correct answer
In a different exam question asking about the effects of configuring an interface as passive in OSPF, if the question stated that the passive interface would stop all OSPF processes on the router, then this option could be correct if the context was about a misconfigured router where all interfaces were set to passive.
Why candidates choose this
The term 'passive' might imply that the interface is completely inactive in OSPF, leading students to think OSPF is disabled on the entire router. In reality, only hello exchange is stopped on that interface.
✗The passive interface converts OSPF into EIGRP on that linkWrong answer — click to see why▾
Why this is wrong here
The passive-interface command is specific to OSPF and does not change the routing protocol. OSPF remains OSPF; it simply stops sending hellos on that interface. EIGRP has its own passive-interface command with similar behavior but does not convert protocols.
★ When this WOULD be the correct answer
In a different question, if it asked about a scenario where a routing protocol can be changed or configured to operate differently on a specific interface, one might mistakenly think that a command could convert OSPF to EIGRP, leading to this option being perceived as correct.
Why candidates choose this
Students might think that because the interface stops sending OSPF hellos, it might switch to another protocol like EIGRP. However, passive-interface only affects hello behavior and does not alter the routing protocol itself.
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
Don't assume 'passive' means the interface is ignored; it still advertises its network.
Detailed technical explanation
How to think about this question
In OSPF (Open Shortest Path First), a passive interface is configured to stop sending OSPF hello packets on that interface, which prevents the formation of OSPF neighbor adjacencies over that link. However, the interface’s connected network is still advertised into the OSPF routing domain. This means the router informs other OSPF routers about the network reachable via the passive interface without actively participating in OSPF neighbor discovery or adjacency formation on that link.
The decision to configure an interface as passive is based on the need to advertise the connected network while avoiding unnecessary OSPF overhead or security risks on interfaces where no OSPF neighbors should exist, such as user-facing LAN ports or stub networks. The router continues to include the passive interface’s network in its Link State Advertisements (LSAs), allowing other routers to learn about the network without requiring OSPF hello exchanges or adjacency formation on that interface.
A common exam trap is assuming that passive interface means the network is not advertised or that OSPF is disabled entirely on that interface. In reality, passive interfaces still advertise their connected networks but do not form neighbor relationships. This distinction is critical for network design and security, as it allows controlled advertisement without exposing OSPF to unnecessary or untrusted neighbors. Practically, passive interfaces reduce OSPF traffic and prevent unwanted neighbor adjacencies while maintaining accurate routing information.
KKey Concepts to Remember
A passive interface in OSPF prevents sending hello packets and forming neighbor adjacencies on that interface while still advertising the connected network.
OSPF routers advertise networks on passive interfaces through Link State Advertisements even though no OSPF neighbor is formed on those interfaces.
Configuring an interface as passive is useful on user-facing or stub interfaces where OSPF neighbor relationships are unnecessary or undesirable.
Passive interfaces reduce OSPF protocol overhead by stopping hello packet exchanges without disabling OSPF routing on the router.
The passive interface setting does not affect the router ID or OSPF operation on other active interfaces.
OSPF continues to run normally on other interfaces, forming adjacencies and exchanging routing information despite passive interfaces.
A common mistake is to assume passive means the network is not advertised, but OSPF still advertises the network to other routers.
Passive interfaces enhance network security by preventing OSPF neighbor formation on interfaces connected to untrusted or end-user devices.
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
A passive interface in OSPF prevents sending hello packets and forming neighbor adjacencies on that interface while still advertising the connected network.
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 a passive interface in OSPF prevents sending hello packets and forming neighbor adjacencies on that interface while still advertising the connected network., then practise related 200-301 questions on the same topic to reinforce the concept.
IP Routing — This question tests IP Routing — A passive interface in OSPF prevents sending hello packets and forming neighbor adjacencies on that interface while still advertising the connected network..
What is the correct answer to this question?
The correct answer is: The connected network can still be advertised into OSPF through other active adjacencies — A passive interface still matters because the connected network can still be advertised into OSPF even though the interface itself does not form neighbor relationships. In plain language, the router is saying, “This network is mine, and I want others to know about it, but I do not want to speak OSPF directly on this interface.” That is useful on user-facing or stub-like interfaces where no OSPF neighbor should exist.
This distinction is important because some engineers assume passive means “ignored entirely.” It does not. The connected network can still appear in routing updates sent through real neighbors on other interfaces. What changes is neighbor formation on the passive interface itself.
What should I do if I get this 200-301 question wrong?
Review a passive interface in OSPF prevents sending hello packets and forming neighbor adjacencies on that interface while still advertising the connected network., then practise related 200-301 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
A passive interface in OSPF prevents sending hello packets and forming neighbor adjacencies on that interface while still advertising the connected network.
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