- A
Set the OSPF priority to 0 on all interfaces of R1.
Setting the OSPF priority to 0 on an interface prevents the router from being elected as DR or BDR. This is a special value that excludes the router from the election process entirely.
- B
Set the OSPF priority to 255 on all interfaces of R1.
Why wrong: Setting the OSPF priority to 255 makes R1 the most likely candidate for DR/BDR, which is the opposite of the desired outcome.
- C
Set the OSPF priority to 1 on all interfaces of R1.
Why wrong: A priority of 1 is the default value and does not prevent R1 from participating in DR/BDR elections; it can still be elected.
- D
Set the OSPF priority to 0 on the loopback interface of R1.
Why wrong: Setting priority on the loopback interface does not affect DR/BDR elections on Ethernet links to R2, R3, and R4. The priority must be set on the actual interfaces participating in OSPF.
Quick Answer
The answer is to set the OSPF priority to 0 on all of R1’s Ethernet interfaces. This configuration works because an OSPF priority of 0 renders the router ineligible to become the Designated Router or Backup Designated Router, effectively preventing it from ever participating in the DR/BDR election process on those segments. On the CCNA 200-301 v2 exam, this question tests your understanding of OSPF election mechanics and the specific behavior of the priority value, often appearing as a straightforward configuration scenario where you must distinguish between preventing election (priority 0) and maximizing election chances (priority 255). A common trap is assuming that setting priority to 0 on a loopback interface will affect physical interfaces, but elections only occur on broadcast multi-access links like Ethernet. Remember the memory tip: “Zero is a hero that says no—priority zero means the router will never be the DR or BDR.”
CCNA IP Routing Practice Question
This 200-301 practice question tests your understanding of ip routing. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
You are connected to R1 via console. R1 is connected to three routers (R2, R3, R4) over Ethernet links, all in OSPF area 0. Due to network topology, R1 should not become the Designated Router (DR) or Backup Designated Router (BDR) on any of its interfaces. You need to configure R1's OSPF priority appropriately to ensure it never participates in DR/BDR elections.
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"never"Why it matters: Absolute qualifier. True only if the statement has zero exceptions — be cautious of options that seem obvious but break down in edge cases.
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 0 on all interfaces of R1.
Setting the OSPF priority to 0 on each Ethernet interface excludes R1 from DR/BDR elections entirely, as a priority of 0 signals that the router is ineligible. In contrast, option B (priority 255) is incorrect because the highest priority makes a router the most likely to become DR/BDR, not prevent it. Option C (priority 1) allows the router to participate in elections and could still become DR/BDR if no higher-priority router exists. Option D is wrong because setting priority to 0 on the loopback interface does not affect the physical Ethernet interfaces where elections occur.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
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 of R1.
Why this is correct
Setting the OSPF priority to 0 on an interface prevents the router from being elected as DR or BDR. This is a special value that excludes the router from the election process entirely.
Clue confirmation
The clue word "never" in the question point toward this answer.
Related concept
OSPF neighbours must agree on key parameters.
- ✗
Set the OSPF priority to 255 on all interfaces of R1.
Why it's wrong here
Setting the OSPF priority to 255 makes R1 the most likely candidate for DR/BDR, which is the opposite of the desired outcome.
- ✗
Set the OSPF priority to 1 on all interfaces of R1.
Why it's wrong here
A priority of 1 is the default value and does not prevent R1 from participating in DR/BDR elections; it can still be elected.
- ✗
Set the OSPF priority to 0 on the loopback interface of R1.
Why it's wrong here
Setting priority on the loopback interface does not affect DR/BDR elections on Ethernet links to R2, R3, and R4. The priority must be set on the actual interfaces participating in OSPF.
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.
✓Set the OSPF priority to 0 on all interfaces of R1.Correct answer▾
Why this is correct
Setting the OSPF priority to 0 on an interface prevents the router from being elected as DR or BDR. This is a special value that excludes the router from the election process entirely.
✗Set the OSPF priority to 255 on all interfaces of R1.Wrong answer — click to see why▾
Why this is wrong here
A priority of 255 is the highest possible value, ensuring the router becomes the DR or BDR, not excluding it.
Why candidates choose this
Candidates may mistakenly think that a high priority prevents election, or they confuse priority with the concept of 'preference'.
✗Set the OSPF priority to 1 on all interfaces of R1.Wrong answer — click to see why▾
Why this is wrong here
Priority 1 is the default and allows the router to be elected if it has the highest priority or Router ID.
Why candidates choose this
Candidates might think that a low priority (like 1) excludes the router, but only 0 does that.
✗Set the OSPF priority to 0 on the loopback interface of R1.Wrong answer — click to see why▾
Why this is wrong here
Loopback interfaces are not used for DR/BDR elections; they are logical interfaces. The priority must be set on the physical interfaces connecting to other routers.
Why candidates choose this
Candidates may think that OSPF priority is a global setting or that loopback interfaces influence elections, but they don't.
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: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
- OSPF neighbours must agree on key parameters.
- Router ID selection can affect neighbour relationships and LSDB output.
- OSPF cost influences the preferred path.
- A route can appear in OSPF information but not become the installed route.
TExam Day Tips
- Check area mismatch first when OSPF adjacency fails.
- Review passive interfaces when a network is advertised but no neighbour forms.
- Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
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.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 200-301 OSPF questions on adjacency and route selection.
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FAQ
Questions learners often ask
What does this 200-301 question test?
IP Routing — This question tests IP Routing — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: Set the OSPF priority to 0 on all interfaces of R1. — Setting the OSPF priority to 0 on each Ethernet interface excludes R1 from DR/BDR elections entirely, as a priority of 0 signals that the router is ineligible. In contrast, option B (priority 255) is incorrect because the highest priority makes a router the most likely to become DR/BDR, not prevent it. Option C (priority 1) allows the router to participate in elections and could still become DR/BDR if no higher-priority router exists. Option D is wrong because setting priority to 0 on the loopback interface does not affect the physical Ethernet interfaces where elections occur.
What should I do if I get this 200-301 question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 200-301 OSPF questions on adjacency and route selection.
Are there clue words in this question I should notice?
Yes — watch for: "never". Absolute qualifier. True only if the statement has zero exceptions — be cautious of options that seem obvious but break down in edge cases.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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Last reviewed: Jun 7, 2026
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