- A
The engineer applied the distance bgp 20 200 200 command, which lowers eBGP AD but not iBGP.
Why wrong: This command sets eBGP to 20, iBGP to 200, and local to 200; iBGP remains 200, so OSPF would still be preferred.
- B
The engineer applied the distance 150 0.0.0.0 255.255.255.255 under the OSPF process, raising OSPF AD to 150.
If OSPF AD is raised to 150, iBGP with AD 200 is still higher, but if OSPF AD is raised above 200, iBGP would be preferred. However, raising OSPF to 150 still leaves OSPF preferred. To make iBGP preferred, OSPF AD must be >200 or iBGP AD lowered. This option is plausible if the engineer raised OSPF AD to 250, but the text says 150, so it's incorrect. Let me adjust: The correct answer should be that the iBGP AD was lowered to 100 via distance bgp 20 100 200.
- C
The engineer applied the distance bgp 20 100 200 command, lowering iBGP AD to 100.
This sets iBGP AD to 100, which is lower than OSPF's 110, so iBGP is preferred.
- D
The OSPF route is a type 5 LSA, which has a higher AD than type 3 LSAs.
Why wrong: OSPF AD is 110 for all routes; type does not affect AD.
300-410 Administrative Distance Practice Question
This 300-410 practice question tests your understanding of administrative distance. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
An engineer is troubleshooting a network where R1 and R2 are running iBGP, and R1 learns the prefix 192.168.1.0/24 from R2 with an AD of 200. R1 also learns the same prefix via OSPF from R3 with AD 110. The engineer notices that R1 uses the iBGP route. What configuration change would cause this?
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
The engineer applied the distance 150 0.0.0.0 255.255.255.255 under the OSPF process, raising OSPF AD to 150.
iBGP routes have an AD of 200 by default, which is higher than OSPF's 110, so OSPF should be preferred. If iBGP is preferred, the AD of iBGP must have been lowered or the OSPF AD raised.
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.
- ✗
The engineer applied the distance bgp 20 200 200 command, which lowers eBGP AD but not iBGP.
- ✓
The engineer applied the distance 150 0.0.0.0 255.255.255.255 under the OSPF process, raising OSPF AD to 150.
Why this is correct
If OSPF AD is raised to 150, iBGP with AD 200 is still higher, but if OSPF AD is raised above 200, iBGP would be preferred. However, raising OSPF to 150 still leaves OSPF preferred. To make iBGP preferred, OSPF AD must be >200 or iBGP AD lowered. This option is plausible if the engineer raised OSPF AD to 250, but the text says 150, so it's incorrect. Let me adjust: The correct answer should be that the iBGP AD was lowered to 100 via distance bgp 20 100 200.
Related concept
OSPF neighbours must agree on key parameters.
- ✓
The engineer applied the distance bgp 20 100 200 command, lowering iBGP AD to 100.
- ✗
The OSPF route is a type 5 LSA, which has a higher AD than type 3 LSAs.
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.
Trap categories for this question
Command / output trap
This command sets eBGP to 20, iBGP to 200, and local to 200; iBGP remains 200, so OSPF would still be preferred.
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 300-410 OSPF questions on adjacency and route selection.
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FAQ
Questions learners often ask
What does this 300-410 question test?
Administrative Distance — This question tests Administrative Distance — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: The engineer applied the distance 150 0.0.0.0 255.255.255.255 under the OSPF process, raising OSPF AD to 150. — iBGP routes have an AD of 200 by default, which is higher than OSPF's 110, so OSPF should be preferred. If iBGP is preferred, the AD of iBGP must have been lowered or the OSPF AD raised.
What should I do if I get this 300-410 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 300-410 OSPF questions on adjacency and route selection.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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Last reviewed: Jun 18, 2026
This 300-410 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 300-410 exam.
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