hardMultiple ChoiceObjective-mapped
300-410 Practice Question: An OSPF network has a multi-access link between…
An OSPF network has a multi-access link between routers R1 and R2. R1 is configured with 'ip ospf network point-to-point' on the interface, while R2 uses the default broadcast network type. R1 shows: 'show ip ospf neighbor' lists R2 as FULL/DR, but R2 shows: 'show ip ospf neighbor' lists R1 as FULL/DROTHER. Traffic from R1 to R2's loopback is fine, but from R2 to R1's loopback is intermittent. What is the root cause?
⚠ Common exam trap
Cisco often tests the misconception that 'ip ospf network point-to-point' only affects hello/dead timers or neighbor state, when in reality it fundamentally changes the OSPF operational model on that link, including DR/BDR election and flooding behavior.
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
✓
R1's point-to-point configuration disables DR/BDR election, but R2 still expects it, causing R1 to ignore R2's LSUs.
R1's 'ip ospf network point-to-point' command disables DR/BDR election on its interface, meaning R1 will not participate in the election and will not form a full adjacency with a DR or BDR. However, R2, using the default broadcast network type, expects a DR/BDR election and elects itself as DR (likely due to higher router ID). R1 sees R2 as FULL/DR because R1 still receives Hellos and forms a neighbor relationship, but R1 ignores LSUs from R2 because R1's point-to-point logic does not recognize the DR as a valid next hop for flooding, causing intermittent reachability to R1's loopback.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
R1's point-to-point configuration disables DR/BDR election, but R2 still expects it, causing R1 to ignore R2's LSUs.
Why this is correct
With mismatched network types, R1 sends packets without a DR, but R2 expects them from the DR, leading to packet loss.
- ✗
R2's DR election is incorrect because it has a higher router ID, but R1 should be the DR.
Why it's wrong here
The issue is network type mismatch, not router ID priority.
- ✗
R1's interface has an MTU mismatch that causes OSPF packets to be dropped.
Why it's wrong here
MTU mismatch would cause adjacency failure, not intermittent connectivity.
- ✗
R2 has a firewall that blocks OSPF packets from R1.
Why it's wrong here
No firewall is mentioned.
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.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 300-410 practice question is part of Courseiva's free Cisco 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 300-410 exam.