The answer is that OSPF DR election is non-preemptive on broadcast networks, meaning a higher priority value alone will not trigger a re-election. This is because once a Designated Router (DR) and Backup Designated Router (BDR) are elected, they remain in those roles until they fail or the OSPF process is reset on the segment—even if a new router with a priority of 255 later joins. On the CCNA 200-301 v2 exam, this concept frequently appears as a trick question where a candidate assumes changing a router’s priority to the maximum will immediately make it the DR, but the non-preemptive nature of the election prevents that. A common trap is forgetting that the election only occurs during the initial adjacency formation or after a DR/BDR failure. To remember this, think of OSPF as a “first come, first served” election: once the DR is chosen, it keeps the job until it leaves, no matter how much higher another router’s priority becomes.
CCNA IP Routing Practice Question
This 200-301 practice question tests your understanding of ip routing. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: oSPF elects a Designated Router (DR) and Backup Designated Router (BDR) on broadcast multiaccess networks to optimize routing update exchanges.. 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.
Exhibit
Current state:
R1 priority 1 - DR
R2 priority 1 - BDR
R3 priority changed from 1 to 200 after adjacency formed
On a broadcast multiaccess segment, R3 has an OSPF priority of 255, but it is in the DROTHER state. Which explanation best fits OSPF behavior?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
DR election is nonpreemptive on broadcast networks
On broadcast networks, OSPF DR and BDR election is not preemptive. If a DR is already elected, giving another router a higher priority later does not force a new election unless the current DR goes down or OSPF is reset on the segment.
Key principle: OSPF elects a Designated Router (DR) and Backup Designated Router (BDR) on broadcast multiaccess networks to optimize routing update exchanges.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
DR election is nonpreemptive on broadcast networks
Why this is correct
Changing priority later does not automatically replace the existing DR.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
OSPF elects a Designated Router (DR) and Backup Designated Router (BDR) on broadcast multiaccess networks to optimize routing update exchanges.
✗
A router cannot become DR if it uses a loopback router ID
In a scenario where the question specifies that OSPF is configured to use loopback interfaces exclusively for router IDs and that the DR election process is limited to routers with physical interfaces only, this option would be correct, as it would imply that a router using a loopback ID cannot become DR.
✗
OSPF priority works only on point-to-point links
Why it's wrong here
Priority matters on broadcast and NBMA segments, not point-to-point.
When this WOULD be correct
If the question specified a scenario where OSPF priority settings were only applicable to point-to-point links and did not mention broadcast networks, then this option could be correct. For example, a question could ask about OSPF behavior in a purely point-to-point topology, where priority settings determine the DR election.
✗
R3's priority is lower than the current DR's priority
Why it's wrong here
Area ID is unrelated to which router becomes DR on that segment.
When this WOULD be correct
In a different question setup where the scenario specifies that only routers in area 1 can participate in DR elections, this option would be correct. For example, if the question stated that R3 is in area 0 while other routers are in area 1, it would not be eligible to become 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.
✓DR election is nonpreemptive on broadcast networksCorrect answer▾
Why this is correct
Changing priority later does not automatically replace the existing DR.
✗A router cannot become DR if it uses a loopback router IDWrong answer — click to see why▾
Why this is wrong here
This option is incorrect because OSPF allows routers to use loopback interfaces as router IDs, and a router can still become the DR regardless of the router ID type, as long as it has the highest priority or is the first to declare itself.
★ When this WOULD be the correct answer
In a scenario where the question specifies that OSPF is configured to use loopback interfaces exclusively for router IDs and that the DR election process is limited to routers with physical interfaces only, this option would be correct, as it would imply that a router using a loopback ID cannot become DR.
Why candidates choose this
Candidates may find this option tempting because they might confuse the role of router IDs with OSPF DR election, leading them to believe that the type of router ID could impact the ability to become DR.
✗OSPF priority works only on point-to-point linksWrong answer — click to see why▾
Why this is wrong here
OSPF priority can be configured on both broadcast and point-to-point links, and it is not limited to point-to-point links only. Therefore, the statement that OSPF priority works only on point-to-point links is incorrect in the context of broadcast networks.
★ When this WOULD be the correct answer
If the question specified a scenario where OSPF priority settings were only applicable to point-to-point links and did not mention broadcast networks, then this option could be correct. For example, a question could ask about OSPF behavior in a purely point-to-point topology, where priority settings determine the DR election.
Why candidates choose this
Candidates may be misled by the specific mention of OSPF priority, thinking it is a unique characteristic of point-to-point links, leading them to overlook its applicability in broadcast environments.
✗R3's priority is lower than the current DR's priorityWrong answer — click to see why▾
Why this is wrong here
This distractor assumes the election is based on current priority values, but OSPF DR election is nonpreemptive; even if R3's priority is higher, it will not become DR unless the current DR fails.
★ When this WOULD be the correct answer
In a different question setup where the scenario specifies that only routers in area 1 can participate in DR elections, this option would be correct. For example, if the question stated that R3 is in area 0 while other routers are in area 1, it would not be eligible to become DR.
Why candidates choose this
Candidates might choose this option due to a misunderstanding of OSPF area functions and their impact on router roles, leading them to believe that area membership directly affects DR election eligibility.
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?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
A common exam trap is assuming that increasing a router's OSPF priority after the DR election will cause it to immediately become the new DR. Many candidates mistakenly believe OSPF DR election is preemptive and that the router with the highest priority always becomes DR instantly. However, OSPF DR election on broadcast networks is nonpreemptive, meaning the current DR remains until it fails or OSPF adjacency resets. This misunderstanding can lead to incorrect answers about why a router with a higher priority remains DROTHER, as in the case of R3 in the question.
Detailed technical explanation
How to think about this question
OSPF (Open Shortest Path First) is a link-state routing protocol that uses a designated router (DR) and backup designated router (BDR) election process on broadcast multiaccess networks to reduce the amount of OSPF routing update traffic. The DR acts as a central point for exchanging OSPF LSAs (Link State Advertisements) among routers on the same segment, improving efficiency and scalability. Routers on the segment elect the DR and BDR based primarily on OSPF priority values and router IDs.
The OSPF DR election process on broadcast networks is nonpreemptive, meaning once a DR is elected, it remains the DR until it goes down or OSPF adjacency resets occur. Even if another router later has a higher priority or a higher router ID, it will not replace the current DR. This behavior prevents constant DR changes and network instability. The election uses priority as the first criterion, and if priorities tie, the highest router ID is used as a tiebreaker.
A common exam trap is assuming that changing a router's OSPF priority dynamically will cause an immediate DR re-election. In reality, the existing DR remains in place until it fails or OSPF is reset on the segment. This nonpreemptive behavior means that a router like R3, despite having a higher priority, stays DROTHER if the current DR is still active. Understanding this helps network engineers predict OSPF behavior and avoid misconfigurations or false assumptions about DR roles during troubleshooting.
KKey Concepts to Remember
OSPF elects a Designated Router (DR) and Backup Designated Router (BDR) on broadcast multiaccess networks to optimize routing update exchanges.
The OSPF DR election process uses router priority as the primary factor and router ID as a tiebreaker when priorities are equal.
Once elected, the OSPF DR remains the DR until it goes down or OSPF adjacency resets, because the election process is nonpreemptive.
Changing a router's OSPF priority after DR election does not trigger a new election or replace the current DR automatically.
Routers with loopback-based router IDs can become DRs; the router ID type does not prevent DR election.
OSPF priority values are relevant only on broadcast and NBMA networks, not on point-to-point links where DR election does not occur.
The OSPF area ID does not influence which router becomes DR on a broadcast segment; DR election is local to the segment.
Understanding OSPF DR election nonpreemptive behavior helps avoid misinterpretation of router roles during network troubleshooting.
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
OSPF elects a Designated Router (DR) and Backup Designated Router (BDR) on broadcast multiaccess networks to optimize routing update exchanges.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
Review oSPF elects a Designated Router (DR) and Backup Designated Router (BDR) on broadcast multiaccess networks to optimize routing update exchanges., then practise related 200-301 questions on the same topic to reinforce the concept.
IP Routing — This question tests IP Routing — OSPF elects a Designated Router (DR) and Backup Designated Router (BDR) on broadcast multiaccess networks to optimize routing update exchanges..
What is the correct answer to this question?
The correct answer is: DR election is nonpreemptive on broadcast networks — On broadcast networks, OSPF DR and BDR election is not preemptive. If a DR is already elected, giving another router a higher priority later does not force a new election unless the current DR goes down or OSPF is reset on the segment.
What should I do if I get this 200-301 question wrong?
Review oSPF elects a Designated Router (DR) and Backup Designated Router (BDR) on broadcast multiaccess networks to optimize routing update exchanges., then practise related 200-301 questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
OSPF elects a Designated Router (DR) and Backup Designated Router (BDR) on broadcast multiaccess networks to optimize routing update exchanges.
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. 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?
hard
A.The OSPF hello and dead intervals on R2 do not match those of other routers on the segment.
B.R2 has an OSPF priority of 255.
C.The OSPF network type on the segment was changed to point-to-point.
✓ D.R2 has an OSPF priority of 0.
Why D: When the DR fails on a broadcast OSPF network, the BDR normally takes over as DR and a new BDR is elected. However, if the BDR's OSPF priority is set to 0, the router is ineligible to become DR or BDR. With the DR down and the BDR ineligible, the remaining routers must hold a fresh election, and the router with the highest non-zero priority (or highest router-ID if priorities tie) becomes the new DR. Therefore, R2's priority of 0 explains why it did not become DR and a new election was triggered.
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