- A
90
Why wrong: 90 is the default AD for EIGRP (internal) routes, not OSPF.
- B
100
Why wrong: 100 is the default AD for IGRP (legacy Cisco protocol), not OSPF.
- C
110
OSPF uses an AD of 110 by default, making it more trusted than RIP (120) but less than EIGRP (90) and external EIGRP (170).
- D
120
Why wrong: 120 is the default AD for RIP (Routing Information Protocol), not OSPF.
Question 40 of 520
N10-009 Network Operations Practice Question
This N10-009 practice question tests your understanding of network operations. 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 administrative distance for OSPF routes on a typical Cisco router?
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
✓
110
Option C is correct because the default administrative distance for OSPF routes on a Cisco router is 110. Administrative distance is a trustworthiness metric used to select the best route when multiple routing protocols provide a route to the same destination; a lower value is preferred. OSPF's default AD of 110 is higher than that of static routes (1) and EIGRP (90/170), but lower than RIP (120) and IS-IS (115).
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.
- ✗
90
When this WOULD be correct
This option would be correct if the question asked for the default administrative distance of EIGRP internal routes on a Cisco router.
- ✗
100
When this WOULD be correct
This option would be correct if the question asked for the default administrative distance of IGRP routes on a Cisco router.
- ✓
110
- ✗
120
When this WOULD be correct
This option would be correct in a question asking for the default administrative distance of RIP routes on a Cisco router, as RIP uses a default AD of 120.
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 N10-009 exam frequently reuses these exact scenarios with slightly different constraints.
✓110Correct answer▾
Why this is correct
OSPF uses an AD of 110 by default, making it more trusted than RIP (120) but less than EIGRP (90) and external EIGRP (170).
✗90Wrong answer — click to see why▾
Why this is wrong here
OSPF has a default administrative distance of 110 on Cisco routers. Option A (90) is the default AD for EIGRP internal routes, not OSPF.
★ When this WOULD be the correct answer
This option would be correct if the question asked for the default administrative distance of EIGRP internal routes on a Cisco router.
Why candidates choose this
Candidates often confuse OSPF's AD with EIGRP's AD because both are common interior gateway protocols, and 90 is a frequently memorized value.
✗100Wrong answer — click to see why▾
Why this is wrong here
OSPF has a default administrative distance of 110 on Cisco routers. Option B (100) is the default for IGRP, not OSPF.
★ When this WOULD be the correct answer
This option would be correct if the question asked for the default administrative distance of IGRP routes on a Cisco router.
Why candidates choose this
Candidates may confuse OSPF with IGRP or EIGRP, as 100 is a common administrative distance for interior routing protocols, leading to a mix-up.
✗120Wrong answer — click to see why▾
Why this is wrong here
The default administrative distance for OSPF on Cisco routers is 110, not 120. 120 is the default distance for RIP routes.
★ When this WOULD be the correct answer
This option would be correct in a question asking for the default administrative distance of RIP routes on a Cisco router, as RIP uses a default AD of 120.
Why candidates choose this
Candidates may confuse OSPF's AD with RIP's AD (120) or misremember the order of common AD values (90 for EIGRP, 110 for OSPF, 120 for RIP).
Analysis generated from the official N10-009blueprint 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: answer the scenario, not the keyword
CompTIA often tests the default administrative distances for OSPF, EIGRP, and RIP, and the trap here is confusing OSPF's AD of 110 with EIGRP's AD of 90 or RIP's AD of 120, especially since OSPF is a link-state protocol while EIGRP is a hybrid, leading candidates to misremember the values.
Detailed technical explanation
How to think about this question
The administrative distance is a Cisco-proprietary mechanism not defined in any RFC; it is a local router setting used to arbitrate between routes from different sources. For OSPF, the default AD of 110 applies to both intra-area and inter-area routes, but OSPF external routes (type 1 and type 2) also use 110 by default. In real-world scenarios, if a router learns the same prefix via OSPF (AD 110) and RIP (AD 120), the OSPF route will be installed in the routing table, even if the RIP route has a better metric.
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.
Visual reference
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
What to study next
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FAQ
Questions learners often ask
What does this N10-009 question test?
Network Operations — This question tests Network Operations — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 110 — Option C is correct because the default administrative distance for OSPF routes on a Cisco router is 110. Administrative distance is a trustworthiness metric used to select the best route when multiple routing protocols provide a route to the same destination; a lower value is preferred. OSPF's default AD of 110 is higher than that of static routes (1) and EIGRP (90/170), but lower than RIP (120) and IS-IS (115).
What should I do if I get this N10-009 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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Last reviewed: Jun 30, 2026
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