Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
A network technician is troubleshooting a router that is not forwarding packets to a remote destination network. The routing table shows a valid route learned via OSPF. The technician can successfully ping the next-hop IP address from the router. However, packets to the destination network are not being forwarded. 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
Best answer
CEF (Cisco Express Forwarding) is disabled or has a corruption
CEF creates a forwarding table based on the routing table. If CEF is disabled or the FIB is corrupt, the router will not forward packets even though the route appears in the routing table.
B
Distractor review
The OSPF neighbor relationship is in the EXSTART state
If the OSPF neighbor is in EXSTART, the adjacency is still forming. However, the routing table already has the route, so the neighbor state should be FULL.
C
Distractor review
The outbound interface has been administratively shut down
If the outbound interface were shutdown, the next-hop would not be reachable. The technician can ping the next-hop, so the interface is up.
D
Distractor review
There is an ACL blocking the return traffic
An ACL blocking return traffic would cause user reports of no connectivity, but the technician is testing forwarding from the router itself. The problem is with the forwarding path, not return traffic.
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.
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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 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: CEF (Cisco Express Forwarding) is disabled or has a corruption — If the route is in the routing table but packets are not being forwarded, the forwarding table (e.g., CEF on Cisco routers) may be corrupted or disabled. This causes a discrepancy between the routing table and the actual forwarding decisions.
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.
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