N10-009 Control plane Practice Question
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?
⚠ Common exam trap
A common mix-up: candidates assume a valid route in the routing table and a successful ping to the next-hop guarantee packet forwarding, but CompTia tests the distinction between the control plane (routing table) and the data plane (forwarding table).
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
✓
Hardware switching/forwarding is disabled or the forwarding table is corrupted
When a router has a valid OSPF-learned route and can ping the next-hop IP but still fails to forward packets, the issue is often with the data plane rather than the control plane. Hardware switching mechanisms (such as fast switching or generic forwarding engines) handle packet forwarding; if they are disabled or the forwarding information base (FIB) becomes corrupted, the router will not forward packets even though the routing table (RIB) is correct. Disabling hardware switching forces the router to use process switching, which can also cause forwarding failures.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Hardware switching/forwarding is disabled or the forwarding table is corrupted
Why this is correct
A router maintains both a routing table (control plane) and a forwarding table (data plane). Even with a valid route in the routing table, if the forwarding table is corrupted or not properly synchronized, packets will not be forwarded. This is a common issue in hardware-based switching.
- ✗
The OSPF neighbor relationship is in the EXSTART state
Why it's wrong here
In OSPF, the EXSTART state is an intermediate stage where routers establish master/slave roles and exchange initial Database Description (DBD) packets. Routes are not exchanged or installed into the routing table until the OSPF neighbor relationship progresses to the FULL state. The presence of a 'valid route' in the routing table, as implied by the question, directly contradicts a neighbor being stuck in the EXSTART state.
When this WOULD be correct
This would be correct in a scenario where the routing table does NOT show a valid OSPF route, and the technician is troubleshooting why OSPF routes are missing. The EXSTART state indicates the routers are exchanging database descriptors but have not yet synchronized, so routes are not installed.
- ✗
The outbound interface has been administratively shut down
Why it's wrong here
If the outbound interface were administratively shut down, it would be completely inactive and unable to send or receive any traffic. This would prevent the router from successfully pinging the next-hop IP address, as no packets could egress the interface. Since the problem statement implies a successful ping to the next-hop, the interface cannot be administratively shut down.
When this WOULD be correct
This option would be correct in a scenario where the router cannot ping the next-hop IP address, and the routing table shows a valid route, but the interface is administratively down, causing all traffic to fail.
- ✗
There is an ACL blocking the return traffic
Why it's wrong here
An Access Control List (ACL) blocking return traffic specifically filters incoming packets destined for the router or its connected networks. The scenario describes a problem where the router is failing to forward packets *outbound* to a destination, despite having a valid route. An ACL affecting inbound return traffic would not prevent the initial outbound forwarding process from occurring.
When this WOULD be correct
An ACL blocking return traffic would be correct if the symptom were that pings from the router to the destination succeed, but traffic from the destination back to the source fails (e.g., asymmetric routing or missing permit statements for return traffic).
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 N10-009 exam frequently reuses these exact scenarios with slightly different constraints.
✓Hardware switching/forwarding is disabled or the forwarding table is corruptedCorrect answer▾
Why this is correct
A router maintains both a routing table (control plane) and a forwarding table (data plane). Even with a valid route in the routing table, if the forwarding table is corrupted or not properly synchronized, packets will not be forwarded. This is a common issue in hardware-based switching.
✗The OSPF neighbor relationship is in the EXSTART stateWrong answer — click to see why▾
Why this is wrong here
The OSPF neighbor relationship being in EXSTART state prevents OSPF adjacency formation, but the routing table already shows a valid OSPF-learned route, indicating the neighbor relationship is fully established (FULL state). Thus, EXSTART is not relevant.
★ When this WOULD be the correct answer
This would be correct in a scenario where the routing table does NOT show a valid OSPF route, and the technician is troubleshooting why OSPF routes are missing. The EXSTART state indicates the routers are exchanging database descriptors but have not yet synchronized, so routes are not installed.
Why candidates choose this
Candidates may confuse OSPF neighbor states and think EXSTART implies a problem with route propagation, not realizing that a valid route in the table means the adjacency is fully established.
✗The outbound interface has been administratively shut downWrong answer — click to see why▾
Why this is wrong here
The outbound interface being administratively shut down would prevent the technician from successfully pinging the next-hop IP address from the router, which contradicts the scenario where the ping succeeds.
★ When this WOULD be the correct answer
This option would be correct in a scenario where the router cannot ping the next-hop IP address, and the routing table shows a valid route, but the interface is administratively down, causing all traffic to fail.
Why candidates choose this
Candidates may think that an administratively shut interface is a common cause of forwarding failures, overlooking that the successful ping to the next-hop IP already rules out this issue.
✗There is an ACL blocking the return trafficWrong answer — click to see why▾
Why this is wrong here
The router can successfully ping the next-hop IP, indicating that outbound traffic is not blocked by an ACL. The issue is with forwarding packets to the destination network, not with return traffic, and the problem persists despite a valid OSPF route and reachable next-hop.
★ When this WOULD be the correct answer
An ACL blocking return traffic would be correct if the symptom were that pings from the router to the destination succeed, but traffic from the destination back to the source fails (e.g., asymmetric routing or missing permit statements for return traffic).
Why candidates choose this
Candidates often confuse outbound and inbound ACLs, or assume that any connectivity issue must be due to an ACL, especially when other obvious causes (like interface status or routing) appear fine.
Analysis generated from the official N10-009blueprint 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
Troubleshooting Methodology
Key term
IP address
An IP address is a unique numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication.
Key term
Route
A route is a path that data takes through a network from one device or network to another, determined by routing protocols and configured rules.
About these practice questions
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This N10-009 practice question is part of Courseiva's free CompTIA 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 N10-009 exam.