- A
The OSPF hello interval is changed to 20 seconds, and the dead interval is changed to 80 seconds, maintaining the default 4:1 ratio.
Correct. The hello interval is set to 20, and dead interval to 80, which is 4 times the hello interval, as required by OSPF.
- B
The OSPF hello interval is changed to 20 seconds, but the dead interval remains at the default of 40 seconds.
Why wrong: Incorrect. The dead interval is explicitly set to 80 seconds, overriding the default.
- C
The OSPF hello interval is changed to 20 seconds, and the dead interval is automatically set to 60 seconds.
Why wrong: Incorrect. The dead interval is explicitly configured as 80 seconds, not automatically derived.
- D
This configuration will cause OSPF adjacency failure because the dead interval must be exactly 4 times the hello interval.
Why wrong: Incorrect. The dead interval is exactly 4 times the hello interval (80 = 4 * 20), so adjacency will form normally.
Quick Answer
The answer is that the OSPF hello interval is changed to 20 seconds and the dead interval to 80 seconds, preserving the default 4:1 ratio. This configuration is correct because OSPF allows manual timer adjustment on a per-interface basis using the `ip ospf hello-interval` and `ip ospf dead-interval` commands; when you set the hello to 20, the dead must be at least four times that value for the adjacency to form, and here it is explicitly set to 80, matching the default multiplier. On the ENCOR 350-401 exam, this tests your understanding that OSPF timers must match between neighbors, but the 4:1 ratio is a default, not a protocol requirement—a common trap is assuming the dead interval automatically adjusts when you change the hello, which it does not. A key memory tip: think of the dead interval as the “four times hello” default, but remember that both values must be explicitly configured if you change either one.
350-401 Network Function Virtualization Practice Question
This 350-401 practice question tests your understanding of network function virtualization. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
Examine the following configuration snippet:
interface GigabitEthernet0/1 ip address 192.168.1.1 255.255.255.0 ip ospf hello-interval 20 ip ospf dead-interval 80
What is the effect of this configuration?
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
The OSPF hello interval is changed to 20 seconds, and the dead interval is changed to 80 seconds, maintaining the default 4:1 ratio.
Option A is correct because the configuration explicitly sets the OSPF hello interval to 20 seconds and the dead interval to 80 seconds, which maintains the default 4:1 ratio (dead = hello × 4). OSPF allows manual configuration of these timers, and as long as both sides of the adjacency match, the ratio can be any value; the 4:1 default is not enforced by the protocol.
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.
- ✓
The OSPF hello interval is changed to 20 seconds, and the dead interval is changed to 80 seconds, maintaining the default 4:1 ratio.
Why this is correct
Correct. The hello interval is set to 20, and dead interval to 80, which is 4 times the hello interval, as required by OSPF.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The OSPF hello interval is changed to 20 seconds, but the dead interval remains at the default of 40 seconds.
Why it's wrong here
Incorrect. The dead interval is explicitly set to 80 seconds, overriding the default.
- ✗
The OSPF hello interval is changed to 20 seconds, and the dead interval is automatically set to 60 seconds.
Why it's wrong here
Incorrect. The dead interval is explicitly configured as 80 seconds, not automatically derived.
- ✗
This configuration will cause OSPF adjacency failure because the dead interval must be exactly 4 times the hello interval.
Why it's wrong here
Incorrect. The dead interval is exactly 4 times the hello interval (80 = 4 * 20), so adjacency will form normally.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that the dead interval must always be exactly 4 times the hello interval, but the actual requirement is that the timers must match between neighbors, not that a specific ratio must be maintained.
Detailed technical explanation
How to think about this question
Under the hood, OSPF hello and dead intervals are advertised in Hello packets, and neighbors must agree on these values to form an adjacency (RFC 2328, Section 10.5). In real-world scenarios, administrators may increase the hello interval to reduce overhead on slow links or to accommodate higher latency, but they must ensure the dead interval is long enough to avoid false neighbor loss. The 4:1 ratio is a Cisco default, not a protocol requirement, and can be changed arbitrarily as long as both sides match.
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.
What to study next
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FAQ
Questions learners often ask
What does this 350-401 question test?
Network Function Virtualization — This question tests Network Function Virtualization — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The OSPF hello interval is changed to 20 seconds, and the dead interval is changed to 80 seconds, maintaining the default 4:1 ratio. — Option A is correct because the configuration explicitly sets the OSPF hello interval to 20 seconds and the dead interval to 80 seconds, which maintains the default 4:1 ratio (dead = hello × 4). OSPF allows manual configuration of these timers, and as long as both sides of the adjacency match, the ratio can be any value; the 4:1 default is not enforced by the protocol.
What should I do if I get this 350-401 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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Last reviewed: Jun 24, 2026
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