Quick Answer
The answer is 110. In Cisco IOS, the default administrative distance for OSPF routes is 110, which is a fundamental metric used by the router’s routing table to determine the trustworthiness of a route when multiple routing protocols compete for the same destination prefix. A lower AD value is preferred, so OSPF’s AD of 110 places it more reliable than RIP (120) and IS-IS (115), but less preferred than static routes (1) or EIGRP internal routes (90). On the Cisco CCNP ENARSI 300-410 exam, this concept often appears in questions about route selection or redistribution, where a common trap is confusing OSPF’s AD with EIGRP’s or forgetting that external OSPF routes use a different AD (170). A quick memory tip: think of OSPF as the “110” emergency number—it’s the default go-to for internal routing, but not as urgent as a static route’s “1.”
This 300-410 practice question tests your understanding of device access control. 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 in Cisco IOS?
90
Why wrong: 90 is the default administrative distance for EIGRP internal routes.
100
Why wrong: 100 is not a standard administrative distance for any common routing protocol in Cisco IOS.
110
Correct. OSPF routes have a default administrative distance of 110.
120
Why wrong: 120 is the default administrative distance for RIP.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
110
OSPF has a default administrative distance (AD) of 110 in Cisco IOS. This value is used by the router to select the best route when multiple routing protocols provide a route to the same destination, with lower AD values being preferred. OSPF's 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
For each option: why learners choose it and why it is or isn't the right answer here.
90
Why it's wrong here
90 is the default administrative distance for EIGRP internal routes.
100
Why it's wrong here
100 is not a standard administrative distance for any common routing protocol in Cisco IOS.
110
Why this is correct
Correct. OSPF routes have a default administrative distance of 110.
Related concept
Read the scenario before looking for a memorised answer.
120
Why it's wrong here
120 is the default administrative distance for RIP.
Common exam traps
Cisco often tests the default administrative distances of OSPF, EIGRP, and RIP together, 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 commonly associated with link-state protocols that are often considered more reliable than distance-vector protocols like RIP.
Detailed technical explanation
The administrative distance is a Cisco-proprietary mechanism used to rank the trustworthiness of routing information sources; it is not defined in any RFC. OSPF's AD of 110 applies to both intra-area and inter-area routes, but external OSPF routes (type 1 and type 2) also use AD 110 by default. In real-world scenarios, if a router learns the same prefix via OSPF (AD 110) and EIGRP (AD 90), the EIGRP route will be installed in the routing table, which can lead to suboptimal routing if not carefully designed.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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
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FAQ
Device Access Control — This question tests Device Access Control — Read the scenario before looking for a memorised answer..
The correct answer is: 110 — OSPF has a default administrative distance (AD) of 110 in Cisco IOS. This value is used by the router to select the best route when multiple routing protocols provide a route to the same destination, with lower AD values being preferred. OSPF's AD of 110 is higher than that of static routes (1) and EIGRP (90/170), but lower than RIP (120) and IS-IS (115).
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 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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