Quick Answer
The answer is 10 seconds. On Ethernet broadcast networks, OSPF defaults to a hello interval of 10 seconds, as specified in RFC 2328, because these high-speed multi-access links require rapid neighbor discovery and failure detection to maintain efficient routing convergence. This interval directly determines the dead interval, which is typically four times the hello interval, or 40 seconds, meaning a router will declare a neighbor down if no hello is received within that window. On the ENCOR 350-401 exam, this is a foundational OSPF concept often tested in multiple-choice or drag-and-drop scenarios, where a common trap is confusing the 10-second default with the 30-second default used on non-broadcast or point-to-point links like Frame Relay. Remember that broadcast networks are fast and chatty, so the hello interval is short. A simple memory tip: Ethernet is everywhere, and 10 is a nice round number—just think "Ethernet = 10 seconds" to lock it in.
This 350-401 practice question tests your understanding of enterprise network design. 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 hello interval on an Ethernet broadcast network?
10 seconds
The default hello interval for OSPF on broadcast and point-to-point networks is 10 seconds.
30 seconds
Why wrong: 30 seconds is the default for NBMA networks, not Ethernet.
5 seconds
Why wrong: 5 seconds is not a default OSPF hello interval.
20 seconds
Why wrong: 20 seconds is not a default OSPF hello 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
10 seconds
On Ethernet broadcast networks, OSPF defaults to a hello interval of 10 seconds, as specified in RFC 2328. This interval is used to maintain neighbor relationships and detect failures quickly on high-speed multi-access links.
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.
10 seconds
Why this is correct
The default hello interval for OSPF on broadcast and point-to-point networks is 10 seconds.
Related concept
Read the scenario before looking for a memorised answer.
30 seconds
Why it's wrong here
30 seconds is the default for NBMA networks, not Ethernet.
5 seconds
Why it's wrong here
5 seconds is not a default OSPF hello interval.
20 seconds
Why it's wrong here
20 seconds is not a default OSPF hello interval.
Common exam traps
Cisco often tests the OSPF hello interval default by mixing up broadcast and NBMA values, leading candidates to mistakenly choose 30 seconds for Ethernet networks.
Detailed technical explanation
The OSPF hello interval is configured under the 'ip ospf hello-interval' interface command, and the dead interval defaults to 4 times the hello interval (40 seconds on broadcast networks). On point-to-point links, the hello interval is also 10 seconds, but on NBMA networks it is 30 seconds to account for slower or more costly connectivity. Understanding these defaults is critical for troubleshooting OSPF adjacency formation, as mismatched hello or dead intervals prevent neighbors from forming.
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.
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FAQ
Enterprise Network Design — This question tests Enterprise Network Design — Read the scenario before looking for a memorised answer..
The correct answer is: 10 seconds — On Ethernet broadcast networks, OSPF defaults to a hello interval of 10 seconds, as specified in RFC 2328. This interval is used to maintain neighbor relationships and detect failures quickly on high-speed multi-access links.
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 350-401 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 350-401 exam.
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