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350-401 Practice Question: Examine the following partial configuration on a…
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
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What is the effect of this configuration?
⚠ Common exam trap
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.
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.
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.
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
This is correct because OSPF hello and dead intervals are configurable per interface, and once configured with 5 and 20 seconds, the router will use those exact values for sending hello packets and for declaring a neighbor unreachable. The dead interval of 20 seconds is four times the hello interval, maintaining the recommended ratio for OSPF stability and fast convergence. This configuration is valid and commonly used to tune OSPF convergence times on point-to-point links.
- ✗
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
This is incorrect because the configured hello and dead intervals always take precedence over the OSPF defaults; the router will not revert to the default 10-second hello and 40-second dead interval simply because the values are non-default. The explicit interface configuration of 'ip ospf hello-interval 5' and 'ip ospf dead-interval 20' overrides any default settings. Therefore, the router will continue to use the configured timers, not override them.
- ✗
The configuration is invalid because the dead interval must be exactly four times the hello interval.
Why it's wrong here
This is incorrect because OSPF does not enforce a strict requirement that the dead interval be exactly four times the hello interval; it only requires the dead interval to be greater than the hello interval, and Cisco recommends a multiple of four for stability. In fact, the configured dead interval of 20 is exactly four times the hello of 5, so the configuration meets the recommended ratio and is perfectly valid. A router would accept any dead interval greater than the hello interval, as long as neighbors match.
- ✗
The router will not form OSPF adjacencies because the hello and dead intervals are not default.
Why it's wrong here
This is incorrect because OSPF neighbor adjacency requires only that the hello and dead intervals match between the two routers; using non-default values does not prevent adjacency formation. When both interfaces are configured with the same non-default timers (5 and 20), the routers will successfully form an OSPF adjacency. The default timers are simply defaults, not mandated values, so this statement is false.
Visual reference
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.