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.
A network has two equal-cost OSPF paths to 192.168.1.0/24. The engineer wants to enable per-flow load balancing. Which configuration element is required?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add 'multipath' under 'routing-options' for OSPF
ECMP requires enabling the 'multipath' statement under routing-options for the protocol. Option A is correct. Option B is not a typical configuration; per-packet is not recommended. Option C is incorrect because setting a higher preference would break ECMP. Option D is incorrect because the hash-key is optional and not required.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
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 per-packet load balancing under the interface
Why it's wrong here
Per-packet load balancing is not standard for routing protocols in JunOS; per-flow is typical.
✓
Add 'multipath' under 'routing-options' for OSPF
Why this is correct
'multipath' enables ECMP, which allows multiple equal-cost routes to be used.
Define a load-balancing hash-key including Layer 4 information
Why it's wrong here
Hash-key configuration is optional and does not enable ECMP itself.
✗
Set a higher preference on one path to force ECMP
Why it's wrong here
Higher preference makes the route less preferred, not equal.
Common exam traps
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
OSPF neighbours must agree on key parameters.
Router ID selection can affect neighbour relationships and LSDB output.
OSPF cost influences the preferred path.
A route can appear in OSPF information but not become the installed route.
TExam Day Tips
→Check area mismatch first when OSPF adjacency fails.
→Review passive interfaces when a network is advertised but no neighbour forms.
→Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
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.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related JNCIA-JUNOS OSPF questions on adjacency and route selection.
Routing Fundamentals — This question tests Routing Fundamentals — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: Add 'multipath' under 'routing-options' for OSPF — ECMP requires enabling the 'multipath' statement under routing-options for the protocol. Option A is correct. Option B is not a typical configuration; per-packet is not recommended. Option C is incorrect because setting a higher preference would break ECMP. Option D is incorrect because the hash-key is optional and not required.
What should I do if I get this JNCIA-JUNOS question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related JNCIA-JUNOS OSPF questions on adjacency and route selection.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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