hardMultiple ChoiceObjective-mapped
300-410 Practice Question: Router R1 and R2 are OSPF neighbors over a…
Router R1 and R2 are OSPF neighbors over a FastEthernet link with BFD enabled. R1 has 'ip ospf network point-to-point' configured. R2 does not. After a reload, BFD sessions fail to establish. R1#show bfd neighbors shows no sessions. R2#show bfd neighbors shows no sessions. What is the root cause?
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
✓
OSPF network type mismatch between R1 and R2 prevents BFD session establishment.
BFD requires matching OSPF network types on the same link for proper session establishment. When R1 is configured as point-to-point and R2 remains as broadcast, OSPF forms a neighbor relationship but BFD sessions fail because BFD expects consistent interface parameters.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
BFD is not supported on FastEthernet interfaces.
Why it's wrong here
BFD is supported on FastEthernet interfaces.
- ✓
OSPF network type mismatch between R1 and R2 prevents BFD session establishment.
Why this is correct
Mismatched OSPF network types cause BFD to fail because BFD uses interface parameters derived from OSPF network type.
- ✗
BFD timers are not configured globally.
Why it's wrong here
BFD timers can be default; global configuration is not mandatory.
- ✗
OSPF hello/dead intervals must match for BFD to work.
Why it's wrong here
OSPF hello/dead intervals do not directly affect BFD session establishment.
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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