The answer is to configure two static default routes with equal metric values and enable ECMP. This approach works because Equal-Cost Multi-Path (ECMP) allows Junos to install multiple routes with the same preference and metric into the forwarding table, then distribute traffic across them using a hash of source and destination IP addresses and ports. On the JNCIA-Junos exam, this scenario tests your understanding of static routing fundamentals and ECMP behavior, often appearing as a question about load-balancing outbound traffic without dynamic protocols. A common trap is assuming unequal metrics or route preferences will still load-balance, but Junos only activates ECMP when routes are truly equal-cost. Memory tip: think “Equal Metrics, Equal Paths” — if the metrics match, ECMP will dispatch.
JNCIA-JUNOS Routing Fundamentals Practice Question
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 organization has two ISPs and wants to load-balance traffic equally across both links for all outbound traffic. Which routing configuration approach should be used?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure two static default routes with equal metric values and enable ECMP.
Option C is correct because configuring two static default routes with equal metric values and enabling Equal-Cost Multi-Path (ECMP) allows the Juniper device to load-balance outbound traffic equally across both ISP links. ECMP uses per-flow or per-packet load balancing based on the hash of source/destination IP addresses and ports, ensuring traffic is distributed evenly without relying on dynamic routing protocols.
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.
✗
Configure two static default routes with different metric values.
Why it's wrong here
Different metrics cause one route to be preferred, not load balancing.
✗
Configure policy-based routing to match all traffic and forward to both ISPs.
Why it's wrong here
Policy-based routing can work but is more complex and not the standard approach for equal load balancing.
✓
Configure two static default routes with equal metric values and enable ECMP.
Read the scenario before looking for a memorised answer.
✗
Establish BGP sessions with both ISPs and rely on BGP path selection.
Why it's wrong here
BGP typically selects a single best path without ECMP.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse metric (cost) with preference (administrative distance) in Junos, assuming that different metric values still allow load balancing, whereas Junos requires equal metric values for ECMP to activate.
Detailed technical explanation
How to think about this question
In Junos, ECMP for static routes is enabled by default when multiple routes have the same metric (preference) and next-hop address. The load-balancing algorithm uses a hash of the Layer 3 and Layer 4 headers (source/destination IP, protocol, and ports) to distribute flows across the equal-cost paths, ensuring per-flow consistency to avoid packet reordering. In real-world scenarios, if one ISP link has higher bandwidth, you would need to use unequal-cost load balancing or adjust route preferences to achieve proportional distribution.
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.
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: Configure two static default routes with equal metric values and enable ECMP. — Option C is correct because configuring two static default routes with equal metric values and enabling Equal-Cost Multi-Path (ECMP) allows the Juniper device to load-balance outbound traffic equally across both ISP links. ECMP uses per-flow or per-packet load balancing based on the hash of source/destination IP addresses and ports, ensuring traffic is distributed evenly without relying on dynamic routing protocols.
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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