The answer is 40 seconds. On a Cisco IOS-XE router, the OSPF default dead interval for a broadcast network type is 40 seconds, derived from four times the default hello interval of 10 seconds as specified in RFC 2328. This four-to-one ratio ensures that a neighbor is declared down only after missing four consecutive hello packets, providing stability against transient network issues. For the Cisco CCNP ENARSI 300-410 exam, this timer relationship is a frequent topic in OSPF neighbor formation and failure detection questions, often appearing as a trap where candidates mistakenly recall the hello interval but forget to multiply by four. A common memory tip is to remember the “4x rule” for broadcast networks: the dead interval is always four times the hello interval, so with a 10-second hello, the dead interval is 40 seconds.
300-410 Device Access Control Practice Question
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 dead interval on a Cisco IOS-XE router for OSPF on a broadcast network type?
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 a broadcast network type, OSPF uses a default dead interval of 40 seconds, which is four times the default hello interval of 10 seconds. This relationship is defined in RFC 2328, ensuring that a neighbor is declared down only after missing four consecutive hello packets.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
10 seconds
Why it's wrong here
This is the default hello interval, not the dead interval.
✗
30 seconds
Why it's wrong here
This value is not a standard default for OSPF dead interval on broadcast networks.
✓
40 seconds
Why this is correct
Correct. The dead interval is 4 × hello interval (4 × 10 = 40 seconds) by default on broadcast and point-to-point networks.
Related concept
Read the scenario before looking for a memorised answer.
✗
120 seconds
Why it's wrong here
This is the default dead interval on NBMA networks (hello interval 30 seconds, dead interval 120 seconds).
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the default OSPF timers for different network types, and the trap here is confusing the default dead interval for broadcast (40 seconds) with the default hello interval (10 seconds) or with the dead interval for other network types like NBMA (30 seconds).
Detailed technical explanation
How to think about this question
The dead interval is calculated as the hello interval multiplied by the dead interval multiplier, which defaults to 4 on broadcast networks. This multiplier can be adjusted using the 'ip ospf dead-interval' command, but the default remains 40 seconds. In real-world scenarios, if the dead interval is set too low, flapping links can cause frequent OSPF neighbor resets, while setting it too high delays convergence during link failures.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
Device Access Control — This question tests Device Access Control — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 40 seconds — On a broadcast network type, OSPF uses a default dead interval of 40 seconds, which is four times the default hello interval of 10 seconds. This relationship is defined in RFC 2328, ensuring that a neighbor is declared down only after missing four consecutive hello packets.
What should I do if I get this 300-410 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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