300-410 Layer 3 Technologies Practice Question
A network engineer is configuring OSPF on a Cisco router. The router has two interfaces in Area 0: GigabitEthernet0/0 (10.1.1.1/24) and GigabitEthernet0/1 (10.2.2.1/24). The engineer wants to ensure that the router ID is always 10.1.1.1, regardless of interface status. Which command should be used?
⚠ Common exam trap
The trap here is assuming that the highest loopback or interface IP will always be used as the router ID, but explicit configuration overrides that and ensures persistence.
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
✓
router ospf 1 then router-id 10.1.1.1
The engineer needs a stable OSPF router ID that remains 10.1.1.1 regardless of interface status. The only way to guarantee this is to explicitly configure the router ID under the OSPF process using the 'router-id' command. Relying on interface IP addresses can lead to changes if interfaces are removed or shut down.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
router ospf 1 then router-id 10.1.1.1
Why this is correct
Entering OSPF configuration mode with 'router ospf 1' and then issuing 'router-id 10.1.1.1' explicitly sets the router ID. This method is preferred because it does not depend on interface IP addresses, ensuring the router ID remains 10.1.1.1 even if interfaces change or go down.
- ✗
ospf router-id 10.1.1.1
Why it's wrong here
This is not a valid Cisco IOS command. The correct command to set the OSPF router ID is 'router-id' under the OSPF routing process configuration. This option would result in a syntax error, so it cannot achieve the goal.
- ✗
router-id 10.1.1.1
Why it's wrong here
This command sets the OSPF router ID, but it is not the most robust method because if the interface with that IP is removed, the router ID may change after a reload. The scenario requires a permanent router ID independent of interface status, so this command alone does not guarantee persistence.
- ✗
ip ospf router-id 10.1.1.1
Why it's wrong here
This command is invalid on Cisco IOS. The 'ip ospf' commands are used for interface-level OSPF parameters like cost or priority, but not for setting the router ID. Using this would cause an error and not fulfill the requirement.
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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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
This 300-410 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 300-410 exam.