- A
Metric
Why wrong: Metric is only compared within the same routing protocol.
- B
Route preference
Route preference is used to compare routes from different protocols; lower preference is preferred.
- C
Route origin
Why wrong: Route origin is a BGP attribute and is not used in cross-protocol comparison.
- D
Next-hop reachability
A route is not active if the next-hop is unreachable, regardless of protocol.
- E
Local preference
Why wrong: Local preference is a BGP-specific attribute and is not used across all protocols.
Question 64 of 514
JNCIA-JUNOS Routing Fundamentals Practice Question
This JNCIA-JUNOS practice question tests your understanding of routing fundamentals. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
Which two factors determine whether a route is active for a given destination when multiple routes from different protocols exist? (Choose two.)
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
✓
Route preference
B is correct because Junos uses route preference (administrative distance) as the primary tiebreaker when multiple routing protocols offer routes to the same destination. The route with the lowest preference value is installed into the routing table as the active route. D is correct because even if a route has the best preference, it must have a reachable next hop to be considered active; if the next hop is unreachable, the route is hidden and not used.
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.
- ✗
Metric
Why it's wrong here
Metric is only compared within the same routing protocol.
- ✓
Route preference
Why this is correct
Route preference is used to compare routes from different protocols; lower preference is preferred.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Route origin
Why it's wrong here
Route origin is a BGP attribute and is not used in cross-protocol comparison.
- ✓
Next-hop reachability
Why this is correct
A route is not active if the next-hop is unreachable, regardless of protocol.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Local preference
Why it's wrong here
Local preference is a BGP-specific attribute and is not used across all protocols.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse metric with preference, thinking metric is used to compare routes from different protocols, but Junos uses preference as the first tiebreaker, and metric only applies within the same protocol.
Detailed technical explanation
How to think about this question
Junos assigns a default preference to each protocol (e.g., direct routes: 0, static: 5, OSPF internal: 10, IS-IS Level 1: 15, BGP: 170). When multiple routes exist, the route with the lowest preference is installed; if preferences are equal, the route with the lowest metric is chosen. A route can be hidden if its next hop is unreachable (e.g., due to a failed interface or missing ARP entry), even if it has the best preference, which is visible with 'show route hidden'.
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.
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
What to study next
Got this wrong? Here's your next step.
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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: Route preference — B is correct because Junos uses route preference (administrative distance) as the primary tiebreaker when multiple routing protocols offer routes to the same destination. The route with the lowest preference value is installed into the routing table as the active route. D is correct because even if a route has the best preference, it must have a reachable next hop to be considered active; if the next hop is unreachable, the route is hidden and not used.
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: Jun 24, 2026
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