Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
A network engineer is implementing OSPF on a router. All directly connected neighbors are listed with state FULL, but routes from another area are not appearing in the routing table. Which of the following is the most likely cause?
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
The router is not configured with a router ID
Without a router ID, OSPF would not form neighbors at all, so this cannot be the issue because neighbors are already FULL.
B
Best answer
The router has an ACL blocking inbound OSPF updates
An ACL that blocks OSPF protocol traffic (e.g., IP protocol 89) can prevent Type 3 LSAs from being received, causing inter-area routes to be missing while local adjacencies remain.
C
Distractor review
The router is configured as an ABR but does not have a virtual-link configured
Virtual-links are only required if a non-backbone area is not directly connected to area 0; the scenario does not indicate that situation.
D
Distractor review
The link-state database is corrupted
A corrupted LSDB would likely cause neighbor adjacencies to fail or routes to be inconsistent; given that neighbors are FULL, this is not the most likely cause.
Common exam trap
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Technical deep dive
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
- OSPF neighbours must agree on key parameters.
- Router ID selection can affect neighbour relationships and LSDB output.
- OSPF cost influences the preferred path.
- A route can appear in OSPF information but not become the installed route.
TExam Day Tips
- Check area mismatch first when OSPF adjacency fails.
- Review passive interfaces when a network is advertised but no neighbour forms.
- Use show ip ospf neighbor and show ip route clues carefully.
Related practice questions
Related N10-009 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Network+ network fundamentals practice questions
Practise N10-009 questions linked to Network+ network fundamentals.
Network+ implementation practice questions
Practise N10-009 questions linked to Network+ implementation.
Network+ operations practice questions
Practise N10-009 questions linked to Network+ operations.
Network+ security practice questions
Practise N10-009 questions linked to Network+ security.
Network+ troubleshooting practice questions
Practise N10-009 questions linked to Network+ troubleshooting.
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 network engineer needs to connect two switches located 400 meters apart. The cable run includes high electromagnetic interference from nearby machinery. The engineer decides to use fiber optic cabling. Which transceiver type and fiber combination should be used to ensure the link reaches 400 meters while remaining cost-effective?
Question 2
A network engineer is designing a new switched network and needs to ensure that broadcast traffic from one department does not reach another department's workstations. The engineer plans to use VLANs. Which of the following must be configured on the switches to isolate broadcast domains as intended?
Question 3
A security engineer is configuring a site-to-site VPN between two branch offices. The requirement is to encrypt all traffic between the two networks using IPsec. Which IPsec mode should be used to encrypt the entire IP packet including the original header?
Question 4
A network administrator is connecting two switches to increase bandwidth and provide redundancy. Which technology should be used to combine multiple physical links into a single logical link?
Question 5
A network administrator is experiencing issues where unauthorized devices are offering IP addresses to clients, causing connectivity problems. Which security feature should be enabled on switches to prevent this?
Question 6
A network administrator is troubleshooting a connectivity issue and suspects the problem is related to the physical cabling. At which layer of the OSI model should the administrator begin their investigation?
FAQ
Questions learners often ask
What does this N10-009 question test?
OSPF neighbours must agree on key parameters.
What is the correct answer to this question?
The correct answer is: The router has an ACL blocking inbound OSPF updates — When OSPF neighbors reach FULL state, the link-state database is synchronized. However, if routes from another area are missing, the issue is likely with the propagation of inter-area routes (Type 3 LSAs). An ACL configured to filter OSPF updates can block these LSAs. The router ID is required for OSPF operation but would prevent neighbor formation if missing. Virtual-links are only needed if an area is not directly connected to area 0. A corrupted link-state database is less likely than a simple ACL filter.
What should I do if I get this N10-009 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
Discussion
Loading comments…
Sign in to join the discussion.