Quick Answer
The answer is 40 seconds. On broadcast multi-access networks like Ethernet, the default OSPF dead interval is always four times the hello interval, which defaults to 10 seconds, yielding a dead interval of 40 seconds. This multiplier ensures that a router can miss up to three consecutive hello packets before being declared dead, providing stability against brief network hiccups. For the Cisco CCNP ENARSI 300-410 exam, this concept tests your understanding of OSPF timer relationships on specific network types, often appearing in questions that try to trick you into confusing the default for point-to-point links (where the hello is 10 seconds but the dead interval is also 40 seconds) or for NBMA networks (where timers differ). A common trap is assuming the dead interval is always 30 seconds, but remember: on broadcast and point-to-point links, it’s 40 seconds. Memory tip: think “4x10 = 40” — the dead interval is simply four hellos.
This 300-410 practice question tests your understanding of device access control. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
What is the default OSPF dead interval on a broadcast multi-access network (e.g., Ethernet) when the hello interval is 10 seconds?
40 seconds
The dead interval is 4 * hello interval (10 seconds) = 40 seconds.
30 seconds
Why wrong: 30 seconds would be 3 times the hello interval, which is not the default.
20 seconds
Why wrong: 20 seconds is twice the hello interval; the default multiplier is 4.
10 seconds
Why wrong: 10 seconds is the hello interval, not the dead interval.
Answer choices
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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
40 seconds
Why this is correct
The dead interval is 4 * hello interval (10 seconds) = 40 seconds.
Related concept
Read the scenario before looking for a memorised answer.
30 seconds
Why it's wrong here
30 seconds would be 3 times the hello interval, which is not the default.
20 seconds
Why it's wrong here
20 seconds is twice the hello interval; the default multiplier is 4.
10 seconds
Why it's wrong here
10 seconds is the hello interval, not the dead interval.
Common exam traps
The trap here is that candidates often 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.
Detailed technical explanation
The dead interval is derived from the hello interval using a multiplier that can be configured per interface with the 'ip ospf dead-interval' command. On broadcast and point-to-point networks, the default multiplier is 4, but on NBMA and point-to-multipoint networks, the default multiplier is also 4, though the hello interval differs (30 seconds for NBMA, leading to a 120-second dead interval). In real-world scenarios, mismatched dead intervals between neighbors can prevent adjacency formation, as OSPF requires these timers to match.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
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FAQ
Device Access Control — This question tests Device Access Control — Read the scenario before looking for a memorised answer..
The correct answer is: 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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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.
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