JNCIS-ENT OSPF Practice Question
When calculating OSPF path costs in a network containing high-speed links (such as 10Gbps and 40Gbps interfaces), what default reference bandwidth does Junos use, and what configuration adjustment is typically required to differentiate costs accurately?
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
✓
100 Mbps default; reference bandwidth must be increased to accurately cost high-speed links.
Junos uses a default OSPF reference bandwidth of 100 Mbps (10^8). Because 100 Mbps results in a cost of 1 for any link 100 Mbps or faster, administrators must increase the reference bandwidth (e.g., to 100 Gbps) so that 10G, 40G, and 100G interfaces have distinct, meaningful integer costs.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
100 Mbps default; reference bandwidth must be increased to accurately cost high-speed links.
Why this is correct
Correct. The default reference bandwidth is 100 Mbps, which causes high-speed links to share a minimum cost of 1 unless adjusted.
- ✗
100 Gbps default; reference bandwidth must be decreased for legacy interfaces.
Why it's wrong here
Incorrect. 100 Gbps is not the Junos default reference bandwidth.
- ✗
10 Gbps default; no adjustment is needed for modern networks.
Why it's wrong here
Incorrect. The default reference bandwidth is 100 Mbps, not 10 Gbps.
- ✗
1 Gbps default; interfaces above 1 Gbps are automatically assigned fractional costs.
Why it's wrong here
Incorrect. Junos OSPF costs use integers, and default reference bandwidth is 100 Mbps.
Visual reference
About these practice questions
This JNCIS-ENT question is part of Courseiva's 519-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed August 2026 · checked against the official Juniper Networks exam blueprint
This JNCIS-ENT practice question is part of Courseiva's free Juniper Networks 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 JNCIS-ENT exam.