CCNA IP Routing Practice Question
Which two statements accurately describe passive interfaces in OSPF?
⚠ Common exam trap
A frequent exam trap is assuming that configuring an interface as passive disables OSPF routing on that interface or converts OSPF routes into static routes. Candidates may also mistakenly believe that passive interfaces automatically disable OSPF on all router interfaces or force the interface IP to become the router ID. These misunderstandings arise because passive interfaces stop hello packets but do not disable OSPF or affect router ID selection. Misreading this can lead to incorrect answers about OSPF behavior and network design.
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 suppresses OSPF hello packets on that interface.
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.
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 suppresses OSPF hello packets on that interface.
Why this is correct
Passive-interface in OSPF stops the router from sending or processing OSPF hello packets on that specific interface. Because hello packets are how neighbor adjacencies are discovered and maintained, the router will not form OSPF neighbors on that link, effectively preventing dynamic neighbor relationships while leaving the interface operational.
- ✓
It can still allow the connected network to be advertised into OSPF.
Why this is correct
Even with OSPF passive-interface configured, the connected network on that interface can still be injected into the OSPF link-state database if the interface's subnet is included in a network statement or the interface is under OSPF configuration. Passive mode only suppresses hello packets and adjacency formation; it does not suppress the advertisement of the directly connected route in OSPF LSAs.
- ✗
It converts OSPF on that interface into static routing.
Why it's wrong here
Passive-interface does not change OSPF into static routing; OSPF remains a dynamic link-state routing protocol that exchanges LSAs to build the topology database. Static routes are manually entered and never advertise via OSPF, so this option confuses the passive interface behavior with a completely different routing mechanism.
When this WOULD be correct
If the exam question asked about the behavior of OSPF when configuring interfaces in a scenario where static routes are being used instead of OSPF, then this option could be correct. For example, a question might ask what happens when OSPF is disabled on an interface and static routing is configured instead.
- ✗
It forces the interface IP address to become the router ID.
Why it's wrong here
The router ID is chosen independently from passive-interface settings, based on the highest IPv4 address on a loopback interface, or if no loopback exists, the highest IPv4 address on any active interface, unless explicitly overridden with the router-id command. Configuring passive-interface does not influence that selection process in any way.
When this WOULD be correct
If the exam question asked about the configuration of OSPF and specifically inquired about how to set the router ID based on interface settings, then option D could be correct if the context was about configuring the router ID using the IP address of a specific interface.
- ✗
It disables OSPF on every interface in the router automatically.
Why it's wrong here
Passive-interface only affects the specific interface on which it is configured; it does not automatically disable OSPF on other interfaces. To make all interfaces passive, you would have to use the 'passive-interface default' command, and even then OSPF still runs globally and advertises networks; the interface in question simply stops sending hellos.
When this WOULD be correct
If the exam question asked about a command that disables OSPF on all interfaces simultaneously, such as 'router ospf [process-id] passive-interface default', then this option would be correct as it would imply that all interfaces are set to passive by default.
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 suppresses OSPF hello packets on that interface.Correct answer▾
Why this is correct
Passive-interface in OSPF stops the router from sending or processing OSPF hello packets on that specific interface. Because hello packets are how neighbor adjacencies are discovered and maintained, the router will not form OSPF neighbors on that link, effectively preventing dynamic neighbor relationships while leaving the interface operational.
✗It converts OSPF on that interface into static routing.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because passive interfaces in OSPF do not convert OSPF routing to static routing; they simply prevent OSPF hello packets from being sent on that interface while still allowing the connected network to be advertised.
★ When this WOULD be the correct answer
If the exam question asked about the behavior of OSPF when configuring interfaces in a scenario where static routes are being used instead of OSPF, then this option could be correct. For example, a question might ask what happens when OSPF is disabled on an interface and static routing is configured instead.
Why candidates choose this
Candidates may find this option tempting because they might confuse the concept of passive interfaces with static routing configurations, leading them to think that passive interfaces somehow change the routing method on that interface.
✗It forces the interface IP address to become the router ID.Wrong answer — click to see why▾
Why this is wrong here
Option D is incorrect because passive interfaces do not change the router ID; the router ID is determined by the highest IP address on an active interface or can be manually configured.
★ When this WOULD be the correct answer
If the exam question asked about the configuration of OSPF and specifically inquired about how to set the router ID based on interface settings, then option D could be correct if the context was about configuring the router ID using the IP address of a specific interface.
Why candidates choose this
Candidates may find this option tempting because they might confuse the concept of passive interfaces with the broader topic of OSPF configuration, leading them to mistakenly believe that it directly influences the router ID.
✗It disables OSPF on every interface in the router automatically.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because configuring a passive interface in OSPF only affects the specified interface, preventing OSPF from sending or receiving hello packets, while other interfaces remain unaffected.
★ When this WOULD be the correct answer
If the exam question asked about a command that disables OSPF on all interfaces simultaneously, such as 'router ospf [process-id] passive-interface default', then this option would be correct as it would imply that all interfaces are set to passive by default.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of how passive interfaces operate, conflating the concept with a broader disabling of OSPF across the router's interfaces.
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
OSPF
OSPF is a link-state routing protocol used to find the best path for data packets to travel across IP networks, like a smart GPS that recalculates routes when traffic changes.
Key term
Router
A router is a networking device that connects different networks together and directs data traffic between them by choosing the best path for data to travel.
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JA
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.