- A
It uses active/passive selection.
Why wrong: Active/passive is not a default behavior; both routes are active if equal.
- B
It load balances via ECMP.
Equal-cost multipath is enabled by default for static routes with equal preferences.
- C
It uses only the first configured route.
Why wrong: Junos does not prioritize by configuration order; it installs both if equal.
- D
It drops traffic due to ambiguity.
Why wrong: Traffic is not dropped; load balancing is applied.
Question 420 of 514
Static Route ECMP: Automatic Load Balancing | JNCIA-Junos
This JNCIA-JUNOS practice question tests your understanding of routing fundamentals. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
An engineer configures two static routes to 172.16.0.0/16 with next-hops 10.0.1.1 and 10.0.2.1, both with the same preference and same metric. How does Junos handle traffic to this prefix?
Quick Answer
The answer is that Junos automatically load balances traffic across both next-hops using ECMP. This occurs because the two static routes to 172.16.0.0/16 share the same preference and metric, making them equal-cost paths in the routing table. Junos enables equal-cost multipath (ECMP) by default for static routes, so traffic is distributed across both 10.0.1.1 and 10.0.2.1 without any additional configuration. On the JNCIA-Junos exam, this concept tests your understanding of how Junos evaluates route selection and forwarding behavior when multiple paths are identical. A common trap is assuming one route becomes active and the other passive, but Junos does not use active/passive by default—it actively uses all equal-cost paths. Remember the memory tip: “Same pref and metric? ECMP is automatic.” This ensures you avoid the pitfall of thinking only one route is installed or that traffic is dropped.
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
✓
It load balances via ECMP.
Junos uses Equal-Cost Multipath (ECMP) when multiple static routes to the same destination prefix have identical preference (administrative distance) and metric. Since both routes to 172.16.0.0/16 have the same preference (default 5 for static routes) and metric (0 by default), Junos installs both in the forwarding table and load-balances traffic across the two next-hops (10.0.1.1 and 10.0.2.1) per-flow or per-packet depending on the configured hash algorithm.
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.
- ✗
It uses active/passive selection.
Why it's wrong here
Active/passive is not a default behavior; both routes are active if equal.
- ✓
It load balances via ECMP.
Why this is correct
Equal-cost multipath is enabled by default for static routes with equal preferences.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
It uses only the first configured route.
Why it's wrong here
Junos does not prioritize by configuration order; it installs both if equal.
- ✗
It drops traffic due to ambiguity.
Why it's wrong here
Traffic is not dropped; load balancing is applied.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates from a Cisco background often assume that only one static route can be active (like Cisco's behavior where the first route is used unless the next-hop fails), but Junos inherently supports ECMP for multiple static routes with equal metrics and preferences.
Detailed technical explanation
How to think about this question
Under the hood, Junos maintains separate routing (RIB) and forwarding (FIB) tables; when multiple static routes have equal preference and metric, they are all placed in the RIB and then programmed into the FIB as a multipath next-hop group. The default ECMP hash algorithm uses source and destination IP addresses to select a next-hop, ensuring per-flow load balancing, which prevents packet reordering. In real-world scenarios, this allows efficient use of multiple uplinks without requiring dynamic routing protocols.
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 practitioner preparing for the JNCIA-JUNOS exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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.
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Routing Fundamentals — study guide chapter
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FAQ
Questions learners often ask
What does this JNCIA-JUNOS question test?
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: It load balances via ECMP. — Junos uses Equal-Cost Multipath (ECMP) when multiple static routes to the same destination prefix have identical preference (administrative distance) and metric. Since both routes to 172.16.0.0/16 have the same preference (default 5 for static routes) and metric (0 by default), Junos installs both in the forwarding table and load-balances traffic across the two next-hops (10.0.1.1 and 10.0.2.1) per-flow or per-packet depending on the configured hash algorithm.
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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Last reviewed: Jul 4, 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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