easyMultiple Choice
300-410 Practice Question: The default OSPF dead interval on a broadcast…
What is the default OSPF dead interval on a broadcast multi-access network (e.g., Ethernet) when the hello interval is 10 seconds?
⚠ Common exam trap
Many exam-takers confuse the default dead interval multiplier (thinking it is 3 instead of 4) or mistakenly apply the NBMA dead interval logic to broadcast networks, leading them to select 30 or 20 seconds.
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
✓
40 seconds
On broadcast multi-access networks like Ethernet, OSPF defaults to a hello interval of 10 seconds. The dead interval is calculated as 4 times the hello interval, resulting in a default dead interval of 40 seconds. This ensures that a router has multiple missed hello opportunities before being declared dead, providing stability against transient network issues.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
40 seconds
Why this is correct
OSPF derives the dead interval as four times the hello interval. With a hello interval of 10 seconds on a broadcast multi-access Ethernet segment, the default dead interval is 40 seconds, matching the stated scenario parameters exactly.
- ✗
30 seconds
Why it's wrong here
The OSPF dead interval defaults to four times the hello interval, giving 40 seconds when hello is 10; 30 seconds corresponds to a hello interval of 7.5 seconds. Thirty seconds would be correct only if the configured hello interval were 7.5 seconds.
- ✗
20 seconds
Why it's wrong here
OSPF derives the dead interval as four times the hello interval, so a 10-second hello yields 40 seconds, not 20. Doubling the hello interval is a tempting shortcut, but that ratio applies to no OSPF timer relationship; 20 seconds would only arise if the hello interval were 5 seconds.
- ✗
10 seconds
Why it's wrong here
The dead interval must be four times the hello interval, giving 40 seconds here; 10 seconds merely echoes the hello value. Matching the two timers is tempting because it appears consistent, yet a router would declare neighbours dead before a single hello cycle completed, breaking adjacency stability.
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
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.