JN0-106 Routing Fundamentals Practice Question
Which two factors does Junos use to select the best route when multiple routes to the same prefix 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
Junos route selection first compares route preference (administrative distance), so option A is correct because the route with the lower preference value (for example, direct 0, static 5, OSPF 10, RIP 100, BGP 170) wins before any protocol-specific metric is considered. If routes have equal preference, Junos then compares the metric, so option D is correct because the lower metric is preferred within the same protocol or routing table. Options B, C, and E are not the two primary Junos best-route selection factors: next-hop type, hop count, and route age are not used as the general tie-breakers in the Junos route selection algorithm.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Route preference
Why this is correct
Route preference is the first and primary criterion Junos uses to choose the best route to a destination. Each routing protocol is assigned a default preference value (e.g., 10 for OSPF, 20 for static, 170 for BGP), and the route with the lowest preference wins. You can modify these values with routing policy or by setting a custom preference, but the comparison always happens before any metric is examined.
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Next-hop type
Why it's wrong here
Next-hop type (direct, indirect, or local) is a property of how a route is resolved in the forwarding table, not a criterion for route selection. It is determined after the best route has been chosen, based on whether the destination is directly connected or requires an intermediate router. Therefore, next-hop type never breaks a tie between competing routes and is irrelevant to the Junos selection algorithm.
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Number of hops
Why it's wrong here
Junos does not consider hop count as a factor when selecting the best route. For IGPs, path cost is expressed as a metric such as OSPF cost or IS-IS metric, which are configurable and based on link bandwidth or other parameters—not on the number of routers traversed. Even for BGP, the AS path length is a separate attribute, not a hop count, and it only matters if route preferences and metrics are already equal.
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Metric
Why this is correct
If multiple routes to the same prefix share the same route preference, Junos then compares the metric, and the route with the lowest metric is selected. The metric is protocol-specific: OSPF uses a cumulative cost, RIP uses hop count (which is actually a legitimate metric there), and BGP uses the MED for exterior routes. This is the second tiebreaker, so it only comes into play after preference has not produced a single winner.
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Route age
Why it's wrong here
Route age (how long a route has been in the routing table) is not a tie-breaker in Junos route selection. While some protocols use timers during convergence, such as BGP's route delay for dampening, Junos does not consider age when comparing active routes. A newly learned route can immediately replace an older one if it has a better preference or metric, so age is purely informational.
Visual reference
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.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This JN0-106 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 JN0-106 exam.