JNCIA-JUNOS Junos Configuration Basics Practice Question
This JNCIA-JUNOS practice question tests your understanding of junos configuration basics. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Your company has deployed a Juniper MX router at a branch office. The router has two upstream connections to different ISPs. The configuration currently uses a single static default route to ISP-A. The network team wants to add redundancy so that if ISP-A fails, traffic automatically uses ISP-B. The ISP-B connection is already configured on interface ge-1/0/0 with IP address 203.0.113.2/30. The next-hop IP for ISP-B is 203.0.113.1. The routing table should have a backup default route with a higher metric. Which configuration change meets the requirement?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
set routing-options static route 0.0.0.0/0 next-hop 203.0.113.1 metric 2
Option C is correct because it adds a static default route to ISP-B with a metric of 2, which is higher than the default metric of 0 (or 1 if explicitly set) for the existing route to ISP-A. In Junos, when multiple static routes to the same destination exist, the route with the lower metric (preference) is installed in the routing table. If the primary route fails (e.g., interface down), the route with the higher metric becomes active, providing automatic failover.
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.
✗
set routing-options static route 0.0.0.0/0 next-hop 203.0.113.1 metric 1
Why it's wrong here
This would create a route with the same metric as the primary, causing ECMP or unpredictability, not a backup.
✗
set routing-options static route 0.0.0.0/0 discard
Why it's wrong here
'discard' drops traffic, not forwards it to ISP-B.
✓
set routing-options static route 0.0.0.0/0 next-hop 203.0.113.1 metric 2
Why this is correct
This creates a backup static route with a higher metric, ensuring it is used only when the primary route is removed.
Related concept
Read the scenario before looking for a memorised answer.
✗
set routing-options static route 0.0.0.0/0 next-table inet.0
Why it's wrong here
'next-table' is used for policy-based routing, not for adding a backup default route.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse Junos 'metric' with Cisco's 'administrative distance' or 'metric' concept, assuming a lower metric is better for backup, whereas in Junos a higher metric (preference) value makes the route less preferred and suitable for failover.
Detailed technical explanation
How to think about this question
In Junos, static routes have a default preference (administrative distance) of 5, but the 'metric' parameter in the 'static route' hierarchy actually sets the preference value, not a routing metric like in OSPF. A lower preference value is preferred; thus, setting metric 2 makes the backup route less preferred than the primary route (which defaults to preference 0 if no metric is set). When the primary route's next-hop becomes unreachable (e.g., interface down), Junos withdraws the route from the routing table, and the backup route with higher preference is installed. This behavior is governed by Junos route selection logic, which compares preference first, then metric (if equal preference).
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
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.
Junos Configuration Basics — This question tests Junos Configuration Basics — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: set routing-options static route 0.0.0.0/0 next-hop 203.0.113.1 metric 2 — Option C is correct because it adds a static default route to ISP-B with a metric of 2, which is higher than the default metric of 0 (or 1 if explicitly set) for the existing route to ISP-A. In Junos, when multiple static routes to the same destination exist, the route with the lower metric (preference) is installed in the routing table. If the primary route fails (e.g., interface down), the route with the higher metric becomes active, providing automatic failover.
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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Question Discussion
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