300-410 Layer 3 Technologies Practice Question
A network engineer is configuring OSPF on a router that connects to a broadcast Ethernet segment. The router is connected to a switch that also connects to three other OSPF routers. The engineer wants to ensure that this router does not become the Designated Router (DR) or Backup Designated Router (BDR) on this segment, but still participates in OSPF. Which configuration should the engineer apply on the router's interface?
⚠ Common exam trap
Many candidates confuse OSPF priority with other interface parameters, or assuming that a high priority prevents DR election rather than encourages it.
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
✓
ip ospf priority 0
The OSPF priority value is used in the DR/BDR election on broadcast and non-broadcast multi-access segments. A priority of 0 makes the router ineligible to become DR or BDR, while still allowing it to form adjacencies and exchange routing information. This is the correct way to keep a router as a DROTHER on a segment where it should not take on a primary role.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
ip ospf database-filter all out
Why it's wrong here
The database-filter all out command is used to filter outbound Link State Advertisements (LSAs) on an interface, typically for demand circuits or to reduce flooding. It does not influence DR/BDR election and would not prevent the router from becoming DR or BDR. It could disrupt OSPF database synchronization if applied incorrectly.
- ✗
ip ospf priority 255
Why it's wrong here
Setting the OSPF priority to 255 makes the router the most likely candidate to become DR, which is the opposite of the requirement. Priority values range from 0 to 255, with higher values increasing the chance of election. A priority of 255 is the maximum and would almost certainly cause this router to be elected DR if it has the highest priority on the segment.
- ✓
ip ospf priority 0
Why this is correct
Setting the OSPF priority to 0 on the interface prevents the router from being elected as DR or BDR on that segment. It will still form adjacencies and participate in OSPF as a DROTHER. This is the standard method to ensure a router does not take on the DR/BDR role while remaining an active OSPF participant.
- ✗
ip ospf network point-to-point
Why it's wrong here
Changing the network type to point-to-point eliminates the DR/BDR election entirely, but it also changes the adjacency behavior and is intended for point-to-point links, not broadcast Ethernet segments with multiple routers. On a broadcast segment, this would cause mismatched network types and prevent adjacencies from forming correctly with other routers expecting broadcast.
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.