- A
The router will send OSPF hello packets every 5 seconds and declare a neighbor dead after 20 seconds of no hello.
Correct. The hello interval is 5 seconds, dead interval is 20 seconds, maintaining the 4:1 ratio.
- B
The router will send OSPF hello packets every 10 seconds and declare a neighbor dead after 40 seconds, overriding the configuration.
Why wrong: Incorrect. The configured values override the defaults.
- C
The configuration is invalid because the dead interval must be exactly four times the hello interval.
Why wrong: Incorrect. The 4:1 ratio is a recommendation, not a strict requirement; the configuration is valid.
- D
The router will not form OSPF adjacencies because the hello and dead intervals are not default.
Why wrong: Incorrect. OSPF neighbors must have matching hello and dead intervals, but non-default values are allowed as long as they match on both sides.
Quick Answer
The correct answer is that the router will send OSPF hello packets every 5 seconds and declare a neighbor dead after 20 seconds of no hello. This configuration directly modifies the default OSPF hello and dead interval values on a broadcast network, where the defaults are 10 seconds and 40 seconds respectively; the `ip ospf hello-interval 5` command reduces the hello interval to 5 seconds, and the `ip ospf dead-interval 20` command sets the dead interval to four times that hello interval, which is the standard multiplier. On the ENCOR 350-401 exam, this tests your understanding of OSPF interface-level timers and the critical rule that the dead interval must be a multiple of the hello interval—typically four times—or neighbor adjacency will fail. A common trap is assuming the dead interval defaults to 40 seconds regardless of the hello interval change, but Cisco IOS automatically adjusts the dead interval only if you change the hello interval first without explicitly setting the dead interval. Memory tip: think “Hello times four” for the dead interval, but always verify both commands are explicitly configured to avoid mismatched timers.
CCNP Virtual Machines and Hypervisors Practice Question
This 350-401 practice question tests your understanding of virtual machines and hypervisors. 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 partial configuration on a Cisco IOS-XE device:
interface GigabitEthernet0/1 ip address 10.1.1.1 255.255.255.0 ip ospf hello-interval 5 ip ospf dead-interval 20
!
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 router will send OSPF hello packets every 5 seconds and declare a neighbor dead after 20 seconds of no hello.
Option A is correct because the `ip ospf hello-interval 5` command sets the OSPF hello interval to 5 seconds, and the `ip ospf dead-interval 20` command sets the dead interval to 20 seconds. These per-interface commands override the default hello interval of 10 seconds and dead interval of 40 seconds for broadcast networks, allowing the router to send hello packets every 5 seconds and declare a neighbor dead after 20 seconds of no hello reception.
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 router will send OSPF hello packets every 5 seconds and declare a neighbor dead after 20 seconds of no hello.
Why this is correct
Correct. The hello interval is 5 seconds, dead interval is 20 seconds, maintaining the 4:1 ratio.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The router will send OSPF hello packets every 10 seconds and declare a neighbor dead after 40 seconds, overriding the configuration.
Why it's wrong here
Incorrect. The configured values override the defaults.
- ✗
The configuration is invalid because the dead interval must be exactly four times the hello interval.
Why it's wrong here
Incorrect. The 4:1 ratio is a recommendation, not a strict requirement; the configuration is valid.
- ✗
The router will not form OSPF adjacencies because the hello and dead intervals are not default.
Why it's wrong here
Incorrect. OSPF neighbors must have matching hello and dead intervals, but non-default values are allowed as long as they match on both sides.
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 four times the hello interval, but in reality, while the default ratio is 4:1, you can configure any values as long as they match on neighboring routers.
Detailed technical explanation
How to think about this question
OSPF uses hello packets to discover neighbors and maintain adjacencies; the dead interval is the time after which a neighbor is considered down if no hello is received. On broadcast and point-to-point networks, the default hello interval is 10 seconds and the dead interval is 40 seconds (four times the hello interval), but these can be changed per interface using the `ip ospf hello-interval` and `ip ospf dead-interval` commands. A real-world scenario where this matters is in fast-convergence designs, where reducing the hello and dead intervals (e.g., to 1 second and 4 seconds) allows quicker detection of link failures, though it increases OSPF control-plane overhead.
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?
Virtual Machines and Hypervisors — This question tests Virtual Machines and Hypervisors — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The router will send OSPF hello packets every 5 seconds and declare a neighbor dead after 20 seconds of no hello. — Option A is correct because the `ip ospf hello-interval 5` command sets the OSPF hello interval to 5 seconds, and the `ip ospf dead-interval 20` command sets the dead interval to 20 seconds. These per-interface commands override the default hello interval of 10 seconds and dead interval of 40 seconds for broadcast networks, allowing the router to send hello packets every 5 seconds and declare a neighbor dead after 20 seconds of no hello reception.
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
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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