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.
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 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?
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.
The correct answer is C. Junos supports equal-cost multipath (ECMP) by default for static routes with the same preference and metric. Traffic is load-balanced across both next-hops. Option A is incorrect because active/passive is not default. Option B is incorrect because both routes are considered. Option D is incorrect because traffic is forwarded.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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
Static NAT maps one inside address to one outside address.
✗
It uses only the first configured route.
Why it's wrong here
Junos does not prioritize by configuration order; it installs both if equal.
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related JNCIA-JUNOS NAT questions on configuration and troubleshooting.
Routing Fundamentals — This question tests Routing Fundamentals — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: It load balances via ECMP. — The correct answer is C. Junos supports equal-cost multipath (ECMP) by default for static routes with the same preference and metric. Traffic is load-balanced across both next-hops. Option A is incorrect because active/passive is not default. Option B is incorrect because both routes are considered. Option D is incorrect because traffic is forwarded.
What should I do if I get this JNCIA-JUNOS question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related JNCIA-JUNOS NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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