Quick Answer
The answer is 10 seconds. This is the default OSPF hello interval on Ethernet links because Ethernet is classified as a broadcast multi-access network type under RFC 2328, where OSPF routers send hello packets every 10 seconds to discover neighbors and maintain adjacencies. The dead interval is automatically set to 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 concept tests your understanding of OSPF network types and their default timers—a common trap is confusing Ethernet’s 10-second hello with the 30-second hello used on non-broadcast or point-to-point links like Frame Relay. Remember the mnemonic: “Ethernet is fast, so hello every 10—dead at 40.”
This 350-401 practice question tests your understanding of sd-access architecture. 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 link?
10 seconds
The default hello interval for OSPF on Ethernet (broadcast) is 10 seconds.
30 seconds
Why wrong: 30 seconds is the default hello interval for OSPF on NBMA networks.
40 seconds
Why wrong: 40 seconds is not a standard OSPF hello interval.
5 seconds
Why wrong: 5 seconds is not the default; it can be configured but is not default.
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
The default OSPF hello interval on an Ethernet link is 10 seconds, as specified in RFC 2328. Ethernet is a broadcast multi-access network type, and OSPF uses a 10-second hello interval on such networks to maintain neighbor adjacencies and detect failures within the dead interval (default 40 seconds, or 4 times the hello interval).
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 Ethernet (broadcast) 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 hello interval for OSPF on NBMA networks.
40 seconds
Why it's wrong here
40 seconds is not a standard OSPF hello interval.
5 seconds
Why it's wrong here
5 seconds is not the default; it can be configured but is not default.
Common exam traps
Cisco often tests the confusion between the OSPF hello interval and dead interval, where candidates mistakenly select 40 seconds (the dead interval) instead of 10 seconds (the hello interval) on Ethernet links.
Detailed technical explanation
Under the hood, the OSPF hello interval is tied to the network type configured under the interface; on Ethernet, the default network type is 'broadcast', which enforces a 10-second hello and 40-second dead interval. In real-world scenarios, changing the network type to 'point-to-point' on an Ethernet link (e.g., for faster convergence) reduces the hello interval to 10 seconds as well, but the default remains 10 seconds for broadcast. The hello interval can be manually adjusted with the 'ip ospf hello-interval' command, but the default is fixed per network type.
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
SD-Access Architecture — This question tests SD-Access Architecture — Read the scenario before looking for a memorised answer..
The correct answer is: 10 seconds — The default OSPF hello interval on an Ethernet link is 10 seconds, as specified in RFC 2328. Ethernet is a broadcast multi-access network type, and OSPF uses a 10-second hello interval on such networks to maintain neighbor adjacencies and detect failures within the dead interval (default 40 seconds, or 4 times the hello interval).
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
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