This 350-401 practice question tests your understanding of ospf. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A network engineer is configuring OSPF on a router that has multiple interfaces in the same area. The engineer wants to ensure that the router does not become the designated router (DR) on any of these interfaces. What should the engineer do?
Correct because a priority of 0 means the router will not be elected as DR or BDR.
B
Configure the OSPF network type as point-to-point on all interfaces.
Why wrong: Incorrect because point-to-point network type eliminates DR election entirely, but the question asks to prevent the router from becoming DR, not to eliminate DR election.
C
Use the 'ip ospf dr-priority' command to set a high priority on other routers.
Why wrong: Incorrect because this would not prevent the local router from becoming DR; it only influences election.
D
Configure the router as an ABR.
Why wrong: Incorrect because being an ABR does not affect DR election.
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 0 on all interfaces.
Setting the OSPF priority to 0 on all interfaces prevents the router from participating in the DR/BDR election process. A router with priority 0 will never become the DR or BDR on any segment, regardless of its Router ID or other factors. This is the only method that guarantees the router will not be elected as DR on any interface.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 all interfaces.
Why this is correct
Correct because a priority of 0 means the router will not be elected as DR or BDR.
Related concept
Read the scenario before looking for a memorised answer.
✗
Configure the OSPF network type as point-to-point on all interfaces.
Why it's wrong here
Incorrect because point-to-point network type eliminates DR election entirely, but the question asks to prevent the router from becoming DR, not to eliminate DR election.
✗
Use the 'ip ospf dr-priority' command to set a high priority on other routers.
Why it's wrong here
Incorrect because this would not prevent the local router from becoming DR; it only influences election.
✗
Configure the router as an ABR.
Why it's wrong here
Incorrect because being an ABR does not affect DR election.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse DR/BDR election prevention with network type changes, thinking that point-to-point is the only way to avoid DR election, but the priority 0 method is the direct and correct answer for preventing a specific router from becoming DR without altering the network type.
Detailed technical explanation
How to think about this question
In OSPF, the DR/BDR election is based on the highest OSPF priority (0-255, default 1) and then the highest Router ID. Setting priority to 0 is a definitive way to opt out of the election, as specified in RFC 2328. This is commonly used for routers that should not be central to the network's LSA flooding, such as customer edge routers or routers with limited resources.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
OSPF — This question tests OSPF — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Set the OSPF priority to 0 on all interfaces. — Setting the OSPF priority to 0 on all interfaces prevents the router from participating in the DR/BDR election process. A router with priority 0 will never become the DR or BDR on any segment, regardless of its Router ID or other factors. This is the only method that guarantees the router will not be elected as DR on any interface.
What should I do if I get this 350-401 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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