JNCIA-JUNOS Routing Fundamentals Practice Question
This JNCIA-JUNOS practice question tests your understanding of routing 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.
Exhibit
show route 192.168.1.0/24
inet.0: 15 destinations, 15 routes (15 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
192.168.1.0/24 *[OSPF/10] 01:00:00, metric 20
> to 10.0.0.2 via ge-0/0/0.0
[Static/5] 00:30:00, metric 0
to 10.0.0.3 via ge-0/0/1.0
Refer to the exhibit. Which route is active for the 192.168.1.0/24 prefix?
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 because it is marked with an asterisk.
In JUNOS, the active route for a prefix is determined by the route preference (administrative distance). OSPF has a default preference of 10, while a static route has a default preference of 5. However, the exhibit shows the OSPF route with an asterisk (*), which in JUNOS indicates the active route in the routing table. Since the OSPF route is marked with an asterisk, it is the active route, and the static route is a backup. Option D is correct because the asterisk signifies the active route, and OSPF's preference is higher (less preferred) than the static route's preference, but the asterisk overrides that assumption in this context.
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.
✗
Both routes are active.
Why it's wrong here
Only one route can be active for a prefix.
✗
The static route because it has a lower preference.
Why it's wrong here
The static route (preference 5) is not active; the OSPF route (preference 10) is active.
The OSPF route because it is marked with an asterisk.
Why this is correct
The '*' indicates the active route.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume a static route always wins over OSPF due to its lower preference, but they overlook that the asterisk in JUNOS output directly indicates the active route, and the static route may be inactive due to next-hop unreachability or other validation failures.
Detailed technical explanation
How to think about this question
In JUNOS, the routing table (inet.0) displays the active route with an asterisk (*) next to it, and the route preference determines which route is installed when multiple routes exist for the same prefix. The default preference for OSPF is 10, and for static routes it is 5, so a static route would normally be preferred. However, if the static route's next-hop is unreachable (e.g., due to a down interface or missing ARP entry), the route is not installed, and the OSPF route becomes active. This behavior is governed by the route's validation process, where JUNOS checks reachability before installing a route; this is a common scenario in real-world networks where a static backup route fails over to a dynamic protocol when the static next-hop is unavailable.
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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Routing Fundamentals — This question tests Routing Fundamentals — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The OSPF route because it is marked with an asterisk. — In JUNOS, the active route for a prefix is determined by the route preference (administrative distance). OSPF has a default preference of 10, while a static route has a default preference of 5. However, the exhibit shows the OSPF route with an asterisk (*), which in JUNOS indicates the active route in the routing table. Since the OSPF route is marked with an asterisk, it is the active route, and the static route is a backup. Option D is correct because the asterisk signifies the active route, and OSPF's preference is higher (less preferred) than the static route's preference, but the asterisk overrides that assumption in this context.
What should I do if I get this JNCIA-JUNOS 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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