CCNP Infrastructure Practice Question
A network engineer is configuring OSPF on a multiaccess segment. The design requires that the DR/BDR election be deterministic, with Router A always becoming the DR and Router B always becoming the BDR. Both routers are Cisco IOS devices. Which configuration on Router A ensures it wins the DR election?
⚠ Common exam trap
The trap here is thinking that Router ID is the primary factor in DR election, when priority takes precedence.
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
✓
Set the OSPF priority to 255 on Router A's interface.
To ensure a router becomes DR, its OSPF interface priority must be higher than all other routers on the segment. Priority 255 is the maximum and guarantees victory unless another router also has 255 and a higher Router ID. Setting priority to 0 makes a router ineligible, a higher Router ID on another router would favor that router, and point-to-point network type removes DR/BDR election altogether.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Set the OSPF priority to 0 on Router A's interface.
Why it's wrong here
Priority 0 means the router is ineligible to become DR or BDR. This would prevent Router A from becoming DR, which is the opposite of the requirement. It is used to exclude a router from the election, such as on a router that should only be a DROTHER.
- ✗
Configure a higher Router ID on Router B.
Why it's wrong here
A higher Router ID on Router B would make Router B more likely to win the election if priorities are equal. This would work against the goal of making Router A the DR. The requirement is to ensure Router A wins, so increasing Router B's Router ID is counterproductive.
- ✓
Set the OSPF priority to 255 on Router A's interface.
Why this is correct
OSPF DR/BDR election is based first on interface priority, then on Router ID. The highest priority wins. Priority 255 is the maximum value and ensures Router A has the highest priority on the segment, making it the DR provided no other router has the same priority with a higher Router ID. This is the standard way to force a router to become DR.
- ✗
Set the OSPF network type to point-to-point on Router A's interface.
Why it's wrong here
Changing the network type to point-to-point eliminates the DR/BDR election entirely because point-to-point networks do not elect a DR or BDR. This would not satisfy the requirement for Router A to become DR; it would remove the concept of DR on that interface.
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 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.