Quick Answer
The answer is the OSPF route to 10.1.1.0/25. This is correct because Juniper Junos always selects the route with the longest prefix match when forwarding a packet, regardless of protocol preference or administrative distance. The destination IP 10.1.1.100 falls within the 10.1.1.0/25 range (10.1.1.0 through 10.1.1.127), making it a more specific match than the /24 static route, which covers a broader range up to 10.1.1.255. On the JNCIA-Junos exam, this concept tests your understanding of the longest prefix match routing selection rule, a fundamental principle that overrides other tie-breakers like metric or route type. A common trap is assuming a static route or a route with a lower administrative distance is always preferred, but Junos evaluates prefix length first. Remember the memory tip: “More bits, better fit”—the route with the most network bits in the subnet mask wins every time.
This JNCIA-JUNOS practice question tests your understanding of networking fundamentals. 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.
A router receives a packet with destination IP 10.1.1.100. The routing table contains two entries: a static route to 10.1.1.0/24 via 192.168.1.1, and an OSPF route to 10.1.1.0/25 via 192.168.2.1. Which route will the router use?
The router drops the packet due to a routing conflict
Why wrong: No conflict; the router will use the route with the longest prefix.
The OSPF route to 10.1.1.0/25
The /25 is the longest prefix match.
The static route to 10.1.1.0/24
Why wrong: The /24 is less specific than /25, so it does not win.
Both routes are used for load balancing
Why wrong: Load balancing requires equal-cost routes with the same prefix length.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The OSPF route to 10.1.1.0/25
The router will use the OSPF route to 10.1.1.0/25 because it has a longer prefix length (/25) than the static route (/24). Juniper Junos uses the most specific (longest) prefix match in the routing table, regardless of administrative distance or protocol preference. The destination IP 10.1.1.100 falls within the 10.1.1.0/25 range (10.1.1.0–10.1.1.127), so the /25 route is more specific and thus preferred.
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.
The router drops the packet due to a routing conflict
Why it's wrong here
No conflict; the router will use the route with the longest prefix.
The OSPF route to 10.1.1.0/25
Why this is correct
The /25 is the longest prefix match.
Related concept
Read the scenario before looking for a memorised answer.
The static route to 10.1.1.0/24
Why it's wrong here
The /24 is less specific than /25, so it does not win.
Both routes are used for load balancing
Why it's wrong here
Load balancing requires equal-cost routes with the same prefix length.
Common exam traps
The trap here is that candidates often assume OSPF routes are always preferred over static routes due to administrative distance, but Junos (and all routers) prioritize the longest prefix match first, so a more specific static route would win over a less specific OSPF route.
Detailed technical explanation
In Junos, the route lookup process first performs a longest-prefix match in the forwarding table (FIB), which is derived from the routing table. The OSPF route to 10.1.1.0/25 has a subnet mask of 255.255.255.128, covering addresses 10.1.1.0–10.1.1.127, while the static /24 covers 10.1.1.0–10.1.1.255. Even if the OSPF route had a higher administrative distance (e.g., 110 vs static’s 5), the longest prefix match takes precedence over protocol preference in Junos. This behavior is consistent with RFC 1812 and is fundamental to IP forwarding.
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
Networking Fundamentals — This question tests Networking Fundamentals — Read the scenario before looking for a memorised answer..
The correct answer is: The OSPF route to 10.1.1.0/25 — The router will use the OSPF route to 10.1.1.0/25 because it has a longer prefix length (/25) than the static route (/24). Juniper Junos uses the most specific (longest) prefix match in the routing table, regardless of administrative distance or protocol preference. The destination IP 10.1.1.100 falls within the 10.1.1.0/25 range (10.1.1.0–10.1.1.127), so the /25 route is more specific and thus preferred.
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 JNCIA-JUNOS 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 JNCIA-JUNOS exam.
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