CCNA IP Routing Practice Question
A technician is troubleshooting an OSPF network. On a broadcast segment, R1 is the DR and R2 is the BDR. R1's interface GigabitEthernet0/0 is shut down for maintenance. The technician expects that R2 will assume the DR role, but instead a new DR election occurs and another router is elected DR. What is the most likely cause?
⚠ Common exam trap
Cisco often tests the misconception that the BDR automatically becomes DR when the DR fails, but the BDR only takes over if it has a non-zero priority; otherwise, a new election is triggered.
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
✓
R2 has an OSPF priority of 0.
When the DR (R1) goes down, a new DR election occurs. R2 is the BDR, but if its OSPF priority is 0, it is ineligible to become the DR. Therefore, a new election takes place among the remaining routers with non-zero priorities, and another router wins the DR 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.
- ✗
The OSPF hello and dead intervals on R2 do not match those of other routers on the segment.
Why it's wrong here
Mismatched timers prevent OSPF neighbor adjacency entirely. If this were the case, R2 would never have become BDR in the first place, because it would not have formed a full adjacency with R1. The issue is DR election, not adjacency.
- ✗
R2 has an OSPF priority of 255.
Why it's wrong here
An OSPF priority of 255 is the highest possible and would make R2 the first choice for DR in any election. This would not prevent R2 from becoming DR; it would cause R2 to be elected DR if a new election occurs, exactly the opposite of the observed behavior.
- ✗
The OSPF network type on the segment was changed to point-to-point.
Why it's wrong here
If the network type had been changed to point-to-point, there would be no DR or BDR at all, and R2 would never have been the BDR. The scenario clearly describes a broadcast segment with an existing DR/BDR relationship.
- ✓
R2 has an OSPF priority of 0.
Why this is correct
On a broadcast OSPF network, a priority of 0 makes a router ineligible for DR or BDR election. Even though R2 was the BDR, its priority of 0 prevents it from taking over as DR when R1 fails. Consequently, a new DR election is triggered among the remaining eligible routers, and a router other than R2 becomes the new DR.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓R2 has an OSPF priority of 0.Correct answer▾
Why this is correct
On a broadcast OSPF network, a priority of 0 makes a router ineligible for DR or BDR election. Even though R2 was the BDR, its priority of 0 prevents it from taking over as DR when R1 fails. Consequently, a new DR election is triggered among the remaining eligible routers, and a router other than R2 becomes the new DR.
✗The OSPF hello and dead intervals on R2 do not match those of other routers on the segment.Wrong answer — click to see why▾
Why this is wrong here
Neighbor adjacency failure due to timer mismatch would have prevented R2 from becoming BDR at all.
✗R2 has an OSPF priority of 255.Wrong answer — click to see why▾
Why this is wrong here
High priority increases the chance of being elected DR, not decrease it.
✗The OSPF network type on the segment was changed to point-to-point.Wrong answer — click to see why▾
Why this is wrong here
Point-to-point networks do not have DR/BDR elections, so R2 could not have been BDR.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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.
Go deeper
Related to this question
Learn chapter
Interpreting HSRP and VRRP Operational Status
Key term
Router
A router is a networking device that connects different networks together and directs data traffic between them by choosing the best path for data to travel.
Key term
Segment
A segment is a division of a larger network, such as a collision domain, broadcast domain, or a portion of a TCP data stream, used to organize traffic and improve performance.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 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 200-301 exam.