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Juniper JN0-351 Exam - Topic 7 Question 42 Discussion

Actual exam question for Juniper's JN0-351 exam
Question #: 42
Topic #: 7
[All JN0-351 Questions]

Exhibit.

Which router will become the OSPF BDR if all routers are powered on at the same time?

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Suggested Answer: A

OSPF DR/BDR election is a process that occurs on multi-access data links. It is intended to select two OSPF nodes: one to be acting as the Designated Router (DR), and another to be acting as the Backup Designated Router (BDR). The DR and BDR are responsible for generating network LSAs for the multi-access network and synchronizing the LSDB with other routers on the same network1.

The DR/BDR election is based on two criteria: the OSPF priority and the router ID. The OSPF priority is a value between 0 and 255 that can be configured on each interface participating in OSPF. The default priority is 1. A priority of 0 means that the router will not participate in the election and will never become a DR or BDR. The router with the highest priority will become the DR, and the router with the second highest priority will become the BDR. If there is a tie in priority, then the router ID is used as a tie-breaker. The router ID is a 32-bit number that uniquely identifies each router in an OSPF domain. It can be manually configured or automatically derived from the highest IP address on a loopback interface or any active interface2.

In this scenario, all routers have the same priority of 1, so the router ID will determine the outcome of the election. The router IDs are shown in the exhibit as RID values. The highest RID belongs to R4 (10.10.10.4), so R4 will become the DR. The second highest RID belongs to R3 (10.10.10.3), so R3 will become the BDR.


1: OSPF DR/BDR Election: Process, Configuration, and Tuning 2: OSPF Designated Router (DR) and Backup Designated Router (BDR)

by Margurite at May 01, 2025, 02:40 PM

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Nada
2 months ago
R1 is a solid choice too, but I agree with R2 being BDR.
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Nu
2 months ago
Wait, how does priority even work in OSPF?
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Selene
2 months ago
Definitely R2, priority rules!
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Isabella
3 months ago
R2 has the highest priority, so it should be BDR.
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Yuette
3 months ago
I think R4 might take it instead, not sure though.
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Leota
3 months ago
I recall that the router with the highest priority becomes the BDR, but I can't remember the specific priorities for these routers.
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Phil
3 months ago
I’m confused about how the router IDs play into this. I feel like I need to double-check the rules for BDR selection.
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Janna
4 months ago
I think it might be R2 because it had the highest priority in a similar practice question I did, but I could be wrong.
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Abel
4 months ago
I remember something about OSPF priorities affecting the BDR election, but I’m not sure which router has the highest priority here.
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Dante
4 months ago
This is a good OSPF question. I'll start by identifying the router IDs and then apply the OSPF election process to determine which router will become the BDR.
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Larae
4 months ago
I'm a little confused by this question. The OSPF election process can be a bit complex, and I'm not sure I fully understand how it works when all the routers are powered on simultaneously. I'll need to think this through step-by-step.
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Winfred
4 months ago
Okay, I've got this. The OSPF BDR is elected based on the router ID, which is typically the highest IP address on the router. I just need to figure out which router has the highest IP address in the diagram.
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Junita
5 months ago
Hmm, I'm a bit unsure about this one. The OSPF election process can get a bit tricky, especially when all the routers are powered on at the same time. I'll need to review my notes carefully.
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Billye
5 months ago
This looks like a pretty straightforward OSPF question. I'll need to think through the OSPF election process to determine which router will become the BDR.
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Glory
8 months ago
D) R2 is the correct answer. Duh, it's the second router in the list. Common sense, people!
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Ailene
7 months ago
D) R2 is the correct answer. Duh, it's the second router in the list. Common sense, people!
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Vesta
7 months ago
D) R2
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Corazon
7 months ago
C) R3
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Art
7 months ago
B) R1
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Geoffrey
7 months ago
A) R4
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Lorrine
9 months ago
Wait, is this a trick question? What if they're all powered on at the same time while standing on their heads? Then I'd say R1 is the OSPF BDR, just to be different.
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Rodolfo
8 months ago
User 3: I'm leaning towards R2.
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Raylene
8 months ago
User 2: I would go with R3.
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Viola
8 months ago
User 1: I think it's R4.
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Yolande
9 months ago
Hmm, this is a tricky one. I'll have to say R3, because it's the middle child and we all know middle children just love to be the center of attention.
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Lacey
8 months ago
I disagree, I believe R4 would become the OSPF BDR.
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Antonio
8 months ago
I think R3 would be the OSPF BDR because it's the middle child.
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Fidelia
9 months ago
That's a good point, I didn't consider the priority. R2 could be the BDR then.
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Carin
9 months ago
I disagree, I believe R2 will become the OSPF BDR because it has the highest priority.
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Ming
9 months ago
R4 is the largest router, so it must be the OSPF BDR. Gotta go with option A!
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Pearline
8 months ago
True, we need to check the OSPF priority to determine the BDR.
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Verlene
8 months ago
But what if R1 has a higher OSPF priority than R2?
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Jesus
8 months ago
I think R2 has the highest OSPF priority, so it will become the BDR.
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Ahmed
8 months ago
R4 is not always the largest router, it depends on the OSPF priority. So it could be any router.
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Fidelia
9 months ago
I think it will be R4 because it has the highest router ID.
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Lyla
10 months ago
If all routers are powered on at the same time, then R2 should become the OSPF BDR. That's my guess.
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Bernardine
8 months ago
R2 seems like the best option to me.
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Bobbye
8 months ago
I believe R2 is the correct choice.
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Felix
9 months ago
I think R2 will become the OSPF BDR.
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