Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
A router advertises its LAN network into OSPF, but no OSPF Hellos should be sent toward end-user devices on that LAN. Which configuration approach solves this cleanly?
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
Distractor review
Use ip ospf cost 65535 on the LAN interface
That changes the metric, not whether Hellos are sent.
B
Best answer
Configure the LAN interface as a passive interface in OSPF
Passive interface stops Hellos while still advertising the subnet.
C
Distractor review
Disable OSPF globally and redistribute connected routes
That is unnecessary and far messier.
D
Distractor review
Convert the LAN interface to a loopback
That changes the interface type entirely and is not the normal fix.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is selecting the option to increase the OSPF cost on the LAN interface to prevent Hello packets. While adjusting the cost changes the metric used for route selection, it does not stop the router from sending or receiving OSPF Hellos. Another common mistake is to disable OSPF globally and redistribute connected routes, which is unnecessarily complex and does not address the problem of suppressing Hellos on a specific interface. Additionally, converting the LAN interface to a loopback is irrelevant because loopbacks are logical interfaces used for router IDs and testing, not for controlling OSPF Hello behavior on physical LAN interfaces.
Technical deep dive
How to think about this question
OSPF (Open Shortest Path First) is a link-state routing protocol that uses Hello packets to discover and maintain neighbor relationships on interfaces. These Hello packets are multicast periodically to establish adjacencies and exchange routing information. However, on interfaces connected to end-user devices, such as LAN segments, forming OSPF neighbor adjacencies is unnecessary and can cause unwanted traffic and security concerns. To address this, Cisco IOS provides the passive interface command within OSPF configuration. When an interface is set as passive, the router continues to advertise the connected subnet into the OSPF domain, ensuring that routing information is shared. However, it stops sending and receiving OSPF Hello packets on that interface, preventing neighbor formation. This approach is clean and efficient for LAN interfaces where no OSPF routers exist beyond the local segment. A common exam trap is confusing passive interfaces with simply increasing the OSPF cost or redistributing connected routes globally. Changing the cost affects route selection but does not suppress Hello packets. Similarly, redistributing connected routes is a broader and more complex solution that does not selectively stop Hellos on a specific interface. Loopback interfaces serve different purposes and are not a valid solution for this scenario. Understanding the passive interface concept is critical for proper OSPF design and exam success.
KKey Concepts to Remember
- OSPF passive interface configuration advertises the connected subnet without sending or receiving OSPF Hello packets on that interface.
- OSPF Hello packets are essential for neighbor discovery and adjacency formation but are unnecessary on interfaces connected to end-user LANs.
- Configuring an interface as passive in OSPF prevents unnecessary OSPF traffic toward devices that do not participate in OSPF routing.
- OSPF cost changes on an interface affect route metric calculations but do not stop Hello packet transmission or neighbor formation.
- Redistributing connected routes globally into OSPF is a complex approach that does not selectively suppress Hellos on specific interfaces.
- Loopback interfaces are logical interfaces used for stable router IDs and testing, not for suppressing OSPF Hellos on LAN interfaces.
- A passive interface in OSPF still advertises the subnet to other OSPF routers, ensuring routing information is propagated correctly.
- Using passive interfaces improves network security and efficiency by reducing unnecessary OSPF traffic on user-facing LAN segments.
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?
OSPF passive interface configuration advertises the connected subnet without sending or receiving OSPF Hello packets on that interface.
What is the correct answer to this question?
The correct answer is: Configure the LAN interface as a passive interface in OSPF — A passive interface advertises the connected subnet into OSPF without sending or processing Hellos on that interface. That is exactly what you want for user-facing LANs with no OSPF neighbors.
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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