hardMultiple ChoiceObjective-mapped
300-410 Practice Question: OSPF is configured on a multi-access link between…
OSPF is configured on a multi-access link between R1 and R2. R1 has: interface GigabitEthernet0/0, ip ospf network point-to-point. R2 has default broadcast network type. R1 shows: show ip ospf neighbor includes R2 in FULL state, but R2 shows: show ip ospf neighbor includes R1 in INIT state. What is the root cause?
⚠ Common exam trap
Cisco often tests the asymmetric neighbor state (FULL on one side, INIT on the other) as a signature symptom of OSPF network type mismatch, tempting candidates to blame mismatched process IDs or passive interfaces instead.
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
✓
The network type mismatch causes R1 to use unicast hellos, while R2 expects multicast.
When R1 is configured with 'ip ospf network point-to-point' on a multi-access link, it changes its OSPF behavior to use unicast hellos to the neighbor's IP address instead of the standard multicast address 224.0.0.5. R2, with the default broadcast network type, expects to receive OSPF hellos on the multicast address. Because R1 sends unicast hellos, R2 never receives them, so R2's neighbor state for R1 remains INIT. R1, however, receives R2's multicast hellos and can form a full adjacency from its perspective, leading to the asymmetric state.
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 OSPF process ID does not match R2's.
Why it's wrong here
Process ID mismatch does not affect neighbor state; area ID must match.
- ✓
The network type mismatch causes R1 to use unicast hellos, while R2 expects multicast.
Why this is correct
Point-to-point uses unicast; broadcast uses multicast, leading to one-way communication.
- ✗
R1 has a higher router ID, preventing adjacency.
Why it's wrong here
Router ID affects DR election, not INIT state.
- ✗
R2's interface is passive, blocking OSPF hellos.
Why it's wrong here
Passive interface would prevent any neighbor formation.
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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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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