JN0-106 Routing Fundamentals Practice Question
Which THREE factors influence the selection of the active route in the Junos routing table when multiple routes exist for the same destination? (Choose three.)
⚠ Common exam trap
It's easy for candidates to confuse route preference with metric, thinking both are always compared, but Junos only compares metrics when routes originate from the same protocol (same preference), and never considers interface bandwidth or next-hop count in the selection process.
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 (administrative distance).
Option A is correct because Junos uses route preference (the equivalent of administrative distance) as the primary tiebreaker: when routes to the same destination come from different sources, the route with the lowest preference value (e.g., Direct 0, Static 5, OSPF 10, RIP 100, BGP 170) is installed as active. Option B is correct because the route's originating protocol determines its default preference and thus directly influences which route wins when multiple protocols advertise the same prefix. Option D is correct because when multiple routes come from the same routing protocol (equal preference), Junos compares the metric and selects the route with the lowest metric as active. Option C is not a selection criterion — Junos does not choose a route based on how many next-hops it has; multiple next-hops can be retained for load balancing only after a route is already selected. Option E is not a factor because interface bandwidth is not used as a tiebreaker in the Junos route selection process; metric values are protocol-specific and not derived from raw interface bandwidth.
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 (administrative distance).
Why this is correct
Route preference, also known as administrative distance, is a numerical value assigned to each route by the routing protocol. Junos always prefers a lower preference value, so a route with preference 5 (static) is chosen over a route with preference 10 (OSPF) for the same destination. You can alter these defaults to influence routing decisions. This is the first criterion in Junos route selection process.
- ✓
The routing protocol from which the route originated.
Why this is correct
The routing protocol that originated a route matters because it dictates the default preference value and the nature of the route (e.g., direct, static, dynamic). For example, direct routes have a default preference of 0, static routes 5, and OSPF routes 10, which directly affect which route wins. Furthermore, each protocol carries its own metric and other attributes, but the protocol origin establishes the route's fundamental trust level in Junos.
- ✗
Number of next-hops available for each route.
Why it's wrong here
The number of next-hops listed for a route does not influence which route becomes active, because all routes with at least one valid next-hop are eligible candidates. Junos does not favor a route with more next-hops over one with fewer. After the active route is selected, the system may load-balance across available next-hops, but that decision occurs after the route selection, not during it. Thus, counting next-hops is irrelevant to the active route selection process.
- ✓
Metric value (if from the same routing protocol).
Why this is correct
Metric value is the second-level criterion and only applies when comparing routes that originate from the same protocol and thus share the same preference. Each protocol defines its own metric—OSPF uses cost, RIP uses hop count, and static routes typically have metric 0—and the route with the lower metric is preferred. If metrics are equal, additional tie-breakers like local preference or route learning order come into play, but metric is a key distinguishing factor within a protocol.
- ✗
Bandwidth of the outgoing interface.
Why it's wrong here
The bandwidth of an egress interface is not part of Junos route selection logic; it is never examined when determining the active route. This misconception likely arises from other routing platforms where bandwidth is used as a metric (e.g., EIGRP). However, Junos relies solely on preference and metric, and also considers factors like next-hop reachability and route source interface availability. Interface bandwidth may affect forwarding performance but has no bearing on route preference.
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.