The correct answer is to enter the configuration command set protocols ospf area 0 interface ge-0/0/1 metric 200. This works because OSPF uses a metric based on interface cost, where a lower cost indicates a more preferred path; by raising the metric on ge-0/0/1 to 200, you make that link less attractive than ge-0/0/0, which retains the default OSPF metric of 1 for a Gigabit Ethernet interface, thereby forcing all traffic to the corporate network through core router A and resolving the asymmetric routing issue. On the JNCIA-Junos exam, this scenario tests your understanding of OSPF metric configuration and how to influence path selection without altering routing policies or administrative distances—a common trap is to mistakenly adjust the metric on the preferred interface instead of the less preferred one. Remember the memory tip: “to make a link less liked, raise its metric; to make it more liked, leave it low.”
JNCIA-JUNOS User Interfaces Practice Question
This JNCIA-JUNOS practice question tests your understanding of user interfaces. 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.
You are a junior network engineer at a company that uses Juniper MX routers. You are troubleshooting a connectivity issue on a branch router. The branch router has two upstream links to the corporate network: ge-0/0/0 (10.1.1.1/30, connected to core router A) and ge-0/0/1 (10.1.1.5/30, connected to core router B). The branch router runs OSPF and has a default route learned from both upstream routers. The routing table shows two equal-cost default routes via both next hops. However, traffic from the branch to the corporate network is experiencing intermittent high latency and some packet loss. You suspect that asymmetric routing is causing issues because the return traffic is not following the same path. You want to influence the router to prefer one upstream link for all traffic to the corporate network. You have decided to adjust the OSPF metric on the branch router to make the link to core router A more preferred. You are in configuration mode on the branch router. Which single configuration change will accomplish this goal?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
set protocols ospf area 0 interface ge-0/0/1 metric 200
Option C is correct because setting the OSPFmetric on interface ge-0/0/1 to a higher value (200) increases the cost of that link, making the default route via ge-0/0/0 (which retains the default OSPF metric of 1 on a Gigabit Ethernet interface) more preferred. This influences the branch router to use the lower-cost path through core router A for all traffic to the corporate network, resolving asymmetric routing issues.
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 interfaces ge-0/0/1 unit 0 family inet cost 200
Why it's wrong here
OSPF uses 'metric', not 'cost', to set interface cost.
✗
set protocols ospf area 0 interface ge-0/0/1 passive
Why it's wrong here
Making the interface passive prevents OSPF adjacency, breaking connectivity.
✓
set protocols ospf area 0 interface ge-0/0/1 metric 200
Why this is correct
Increasing the metric on ge-0/0/1 makes it less preferred, so traffic will use ge-0/0/0.
Related concept
Read the scenario before looking for a memorised answer.
✗
set interfaces lo0 unit 0 family inet address 10.0.0.1/32 metric 100
Why it's wrong here
Loopback metric does not affect OSPF path selection for transit traffic.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the 'metric' configuration under the OSPF protocol hierarchy with the 'cost' parameter under interfaces, or mistakenly think that making an interface passive or adjusting loopback metrics will influence OSPF path selection.
Detailed technical explanation
How to think about this question
In OSPF, the metric (cost) of an interface is inversely proportional to bandwidth by default (cost = reference-bandwidth / bandwidth), but can be manually overridden using 'set protocols ospf area <area> interface <interface> metric <value>'. A higher metric makes the link less preferred for outbound traffic, which is key for influencing path selection in equal-cost scenarios. In real-world deployments, adjusting OSPF metrics is a common technique to enforce deterministic routing and avoid asymmetric flows that can cause stateful firewall issues or performance degradation.
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.
User Interfaces — This question tests User Interfaces — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: set protocols ospf area 0 interface ge-0/0/1 metric 200 — Option C is correct because setting the OSPF metric on interface ge-0/0/1 to a higher value (200) increases the cost of that link, making the default route via ge-0/0/0 (which retains the default OSPF metric of 1 on a Gigabit Ethernet interface) more preferred. This influences the branch router to use the lower-cost path through core router A for all traffic to the corporate network, resolving asymmetric routing issues.
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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