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300-410 Practice Question: The default administrative distance for OSPF…
What is the default administrative distance for OSPF routes in Cisco IOS?
⚠ Common exam trap
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.
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
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).
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
Why it's wrong here
A default administrative distance of 90 is assigned to EIGRP internal routes, not OSPF routes. OSPF routes use a default distance of 110, as defined in Cisco IOS for link-state protocols. This option is tempting because 90 is a common administrative distance value, and a candidate might confuse EIGRP’s internal metric with OSPF’s, especially when memorising default distances for dynamic routing protocols. It would be correct only for a question asking about 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.
- ✗
120
Why it's wrong here
An administrative distance of 120 is assigned to RIP routes, not OSPF routes; OSPF uses a default administrative distance of 110 in Cisco IOS. This option is tempting because 120 is a common default distance for dynamic interior gateway protocols, and a candidate might confuse RIP’s metric with OSPF’s when memorising Cisco default values.
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.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.