This 350-401 practice question tests your understanding of ospf. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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 runs the following command on Router R9:
R9# show ip ospf interface brief
Interface PID Area IP Address/Mask Cost State Nbrs F/C
R9 is the Designated Router on the segment connected to Gi0/1.
Why wrong: Gi0/1 is in BDR state, not DR.
B
R9 has two fully adjacent neighbors on Gi0/0.
The Nbrs F/C column shows 2/2, meaning 2 neighbors and 2 full adjacencies.
C
The loopback interface Lo0 is advertised as a /24 network.
Why wrong: The IP address is 9.9.9.9/32, so it is a /32.
D
R9 is an Area Border Router.
Why wrong: Having interfaces in area 0 and area 1 makes it an ABR, but the output does not explicitly state that; however, the question asks what can be concluded from the output, and the neighbor counts are correct.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
R9 has two fully adjacent neighbors on Gi0/0.
The output shows that on interface Gi0/0, R9 has a state of DR (Designated Router) and 2 fully adjacent neighbors (Nbrs F/C = 2/2). The '2/2' indicates 2 neighbors in a full state out of 2 total neighbors, meaning both neighbors have completed the OSPF adjacency process. Therefore, R9 has two fully adjacent neighbors on Gi0/0, making option B correct.
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.
✗
R9 is the Designated Router on the segment connected to Gi0/1.
Why it's wrong here
Gi0/1 is in BDR state, not DR.
✓
R9 has two fully adjacent neighbors on Gi0/0.
Why this is correct
The Nbrs F/C column shows 2/2, meaning 2 neighbors and 2 full adjacencies.
Related concept
Read the scenario before looking for a memorised answer.
✗
The loopback interface Lo0 is advertised as a /24 network.
Why it's wrong here
The IP address is 9.9.9.9/32, so it is a /32.
✗
R9 is an Area Border Router.
Why it's wrong here
Having interfaces in area 0 and area 1 makes it an ABR, but the output does not explicitly state that; however, the question asks what can be concluded from the output, and the neighbor counts are correct.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misinterpretation of the 'Nbrs F/C' field, where candidates confuse the total neighbor count with the number of fully adjacent neighbors, or assume that being in the DR state on one interface implies DR status on all interfaces.
Trap categories for this question
Command / output trap
Having interfaces in area 0 and area 1 makes it an ABR, but the output does not explicitly state that; however, the question asks what can be concluded from the output, and the neighbor counts are correct.
Detailed technical explanation
How to think about this question
In OSPF, the Designated Router (DR) and Backup Designated Router (BDR) election occurs on broadcast multi-access networks (e.g., Ethernet) to reduce LSAs and adjacencies. The 'Nbrs F/C' field shows the number of fully adjacent neighbors (F) out of the total neighbors (C); a value of 2/2 means both neighbors are fully adjacent. The loopback interface is advertised as a /32 host route by default in OSPF, regardless of the configured mask, unless the 'ip ospf network point-to-point' command is used to change its behavior.
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: R9 has two fully adjacent neighbors on Gi0/0. — The output shows that on interface Gi0/0, R9 has a state of DR (Designated Router) and 2 fully adjacent neighbors (Nbrs F/C = 2/2). The '2/2' indicates 2 neighbors in a full state out of 2 total neighbors, meaning both neighbors have completed the OSPF adjacency process. Therefore, R9 has two fully adjacent neighbors on Gi0/0, making option B correct.
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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