mediumMultiple Choice
350-401 Practice Question: Consider the following OSPF configuration on…
Consider the following OSPF configuration on router R2:
interface GigabitEthernet0/0 ip address 192.168.1.2 255.255.255.0 ip ospf 1 area 0 ip ospf hello-interval 5
!
router ospf 1
router-id 2.2.2.2
network 192.168.1.0 0.0.0.255 area 0
Which statement is true about this configuration?
⚠ Common exam trap
Cisco often tests the automatic relationship between the OSPF hello and dead intervals, and the trap here is that candidates assume the dead interval remains at the default value (40 seconds) even after changing the hello interval, rather than understanding it scales proportionally to 4× the new hello interval.
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 dead interval is automatically set to 20 seconds.
The OSPF dead interval is automatically set to four times the hello interval when the hello interval is manually configured. By default, OSPF uses a hello interval of 10 seconds and a dead interval of 40 seconds on broadcast networks. However, when you explicitly set the hello interval to 5 seconds using the 'ip ospf hello-interval 5' command, the router automatically adjusts the dead interval to 20 seconds (4 × 5 seconds) to maintain the standard ratio, unless the dead interval is also manually configured.
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 dead interval is automatically set to 20 seconds.
Why this is correct
When you configure 'ip ospf hello-interval 5' on an interface, Cisco IOS automatically recalculates the OSPF dead interval to four times the hello interval, producing a dead interval of 20 seconds (4 × 5 = 20). This automatic adjustment preserves the default 4-to-1 ratio, ensuring that neighbor hold-down timing remains consistent with the hello interval. To achieve a different dead interval, you would need to explicitly configure 'ip ospf dead-interval'.
- ✗
The OSPF dead interval remains at the default of 40 seconds.
Why it's wrong here
The statement is incorrect because OSPF does not keep the dead interval at 40 seconds when the hello interval is changed. While 40 seconds is the default dead interval for an interface with the default 10-second hello, modifying the hello interval to 5 seconds triggers an automatic recalculation that sets the dead interval to 20 seconds. The dead interval would remain 40 only if you did not change the hello interval or if you explicitly configured a dead interval of 40 with the 'ip ospf dead-interval 40' command.
- ✗
This configuration will cause OSPF to use MD5 authentication.
Why it's wrong here
This configuration does not affect OSPF authentication. The 'ip ospf hello-interval' command only sets the OSPF hello timer; authentication is a separate mechanism controlled by commands such as 'ip ospf authentication', 'ip ospf authentication-key', or 'ip ospf message-digest-key'. MD5 authentication specifically requires the network type and OSPF area to be configured with 'ip ospf message-digest-key' and 'ip ospf authentication message-digest'; changing the hello interval has no bearing on those settings.
- ✗
The OSPF network type changes to point-to-point.
Why it's wrong here
Changing the hello interval does not alter the OSPF network type. The network type is determined by the underlying Layer 2 medium or by the explicit 'ip ospf network' command on the interface; for Ethernet it remains broadcast by default. This means the router continues to use multicast Hello packets (224.0.0.5) and maintains the DR/BDR election process, whereas a point-to-point network type would eliminate DR/BDR elections and use unicast (or multicast 224.0.0.5) differently. Hello-interval changes only affect timing, not the network type or its associated behavior.
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.