Question 1mediummulti select
Full question →mediummulti selectObjective-mapped
Which two statements accurately describe OSPF passive interfaces?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Best answer
It prevents OSPF from sending hello packets on that interface.
This is correct because passive interfaces suppress OSPF hello exchange locally.
B
Best answer
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
Distractor review
It changes OSPF into a static route on that interface.
This is wrong because passive-interface does not convert OSPF into static routing.
D
Distractor review
It forces the interface to become the router ID.
This is wrong because passive-interface does not determine the router ID.
E
Distractor review
It disables OSPF on every interface in the router automatically.
This is wrong because passive-interface affects only the specified interface unless broader defaults are configured.
Common exam trap
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.
Technical deep dive
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.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?
Question 2
A router shows this output: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DR 00:00:34 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 2WAY/DROTHER 00:00:39 192.168.12.3 GigabitEthernet0/0 Which statement is correct?
Question 3
What is the OSPF metric called?
Question 4
A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?
Question 5
A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?
Question 6
A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?
FAQ
Questions learners often ask
What does this 200-301 question test?
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?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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