CCNA IP Routing Practice Question
Why does a passive interface in OSPF still matter even though it does not send hello packets?
⚠ Common exam trap
Don't assume 'passive' means the interface is ignored; it still advertises its network.
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
✓
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.
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
Even when an interface is configured as passive for OSPF, the router still includes that interface's connected subnet in OSPF advertisements, provided the interface is covered by a network statement or under the OSPF process. Passive-interface only disables hello transmission and neighbor discovery on that link, so the prefix is still injected into the LSDB and propagated via active adjacencies on other interfaces.
- ✗
The passive interface automatically becomes the OSPF router ID
Why it's wrong here
The OSPF router ID is chosen from the highest IPv4 address on a loopback interface, then the highest IPv4 address on any active interface, or from the explicit router-id command; a passive-interface setting never participates in this selection process. Making an interface passive neither overrides nor sets the router ID, so this statement is false.
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
Configuring passive-interface only applies to the specified interface, disabling hello transmission and neighbor adjacency formation on that interface while leaving OSPF fully operational on all other interfaces and for the routing process as a whole. Neighbor relationships on active interfaces continue normally, routes are still exchanged, and the router continues to participate in the OSPF domain; therefore OSPF is not entirely disabled.
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
Passive-interface is an OSPF-specific mechanism that suppresses OSPF hello packets while the interface remains entirely under OSPF operation, and it has no effect on the underlying routing protocol identity. OSPF cannot be transformed into EIGRP by any interface keyword; EIGRP is a separate protocol with a distinct administrative distance and algorithm, so this option is incorrect.
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
Even when an interface is configured as passive for OSPF, the router still includes that interface's connected subnet in OSPF advertisements, provided the interface is covered by a network statement or under the OSPF process. Passive-interface only disables hello transmission and neighbor discovery on that link, so the prefix is still injected into the LSDB and propagated via active adjacencies on other interfaces.
✗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?”
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.
Go deeper
Related to this question
Learn chapter
OSPFv3 Single-Area Configuration for IPv6
Key term
Passive interface
A passive interface is a network interface that participates in a routing protocol (like OSPF) by listening for and learning routes, but does not send routing protocol messages out of that interface.
Key term
OSPF neighbor
An OSPF neighbor is another router that has been directly discovered through OSPF Hello packets and is willing to exchange routing information to build a network topology map.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.