Quick Answer
The answer is 100 Mbps. This is the default OSPF reference bandwidth used in the metric calculation on Cisco IOS-XE, where the OSPF cost is derived by dividing this reference bandwidth by the interface bandwidth. Because older Cisco IOS and IOS-XE platforms default to 100 Mbps, a Gigabit Ethernet interface (1,000 Mbps) would receive a cost of 1, while a 10 Gigabit interface would also calculate to 1, making them indistinguishable in metric terms. On the Cisco CCNP ENARSI 300-410 exam, this concept tests your understanding of OSPF path selection and the need to manually adjust the reference bandwidth for high-speed networks using the `auto-cost reference-bandwidth` command. A common trap is assuming the default is 1 Gbps or that it automatically scales with faster interfaces—it does not. Remember the memory tip: “One hundred is the default, or your high-speed links will be dull.”
This 300-410 practice question tests your understanding of ospf troubleshooting (v2/v3). Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
What is the default OSPF reference bandwidth used in the metric calculation on Cisco IOS-XE?
100 Mbps
Correct. The default reference bandwidth is 100 Mbps.
1000 Mbps
Why wrong: Incorrect. 1000 Mbps is not the default; it can be configured using the auto-cost reference-bandwidth command.
10 Mbps
Why wrong: Incorrect. 10 Mbps is not the default reference bandwidth.
10000 Mbps
Why wrong: Incorrect. 10000 Mbps is not the default reference bandwidth.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
100 Mbps
Cisco IOS-XE uses a default reference bandwidth of 100 Mbps for OSPF metric calculation (cost = reference bandwidth / interface bandwidth).
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
100 Mbps
Why this is correct
Correct. The default reference bandwidth is 100 Mbps.
Related concept
OSPF neighbours must agree on key parameters.
1000 Mbps
Why it's wrong here
Incorrect. 1000 Mbps is not the default; it can be configured using the auto-cost reference-bandwidth command.
10 Mbps
Why it's wrong here
Incorrect. 10 Mbps is not the default reference bandwidth.
10000 Mbps
Why it's wrong here
Incorrect. 10000 Mbps is not the default reference bandwidth.
Common exam traps
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
Incorrect. 1000 Mbps is not the default; it can be configured using the auto-cost reference-bandwidth command.
Detailed technical explanation
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.
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
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
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
OSPF Troubleshooting (v2/v3) — This question tests OSPF Troubleshooting (v2/v3) — OSPF neighbours must agree on key parameters..
The correct answer is: 100 Mbps — Cisco IOS-XE uses a default reference bandwidth of 100 Mbps for OSPF metric calculation (cost = reference bandwidth / interface bandwidth).
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.
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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