JN0-106 Routing Fundamentals Practice Question
During a routing table lookup, a packet matches both a static route and an OSPF route to the same destination. Which route will be installed in the forwarding table?
⚠ Common exam trap
Watch out — candidates often assume dynamic protocols like OSPF are always preferred over static routes, but Junos uses preference (administrative distance) where static routes have a lower default value than OSPF, making them more preferred.
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
✓
The static route, because it has a lower preference value.
In Junos, the route with the lowest preference value is installed in the forwarding table. Static routes have a default preference of 5, while OSPF internal routes have a default preference of 10. Therefore, the static route is preferred and installed.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Both routes, if they are equal-cost.
Why it's wrong here
Equal-cost multipath (ECMP) only applies when two routes to the same prefix share the same preference and the same metric. Because a static route defaults to preference 5 and OSPF internal routes default to preference 10, these routes are not equal-cost regardless of their metric values. The router will select the static route as the active route, and no load balancing across both will occur.
- ✗
The route with the higher preference value.
Why it's wrong here
In Junos, preference is an administrative distance that signifies how much the router trusts the source that supplied the route; lower numeric values denote higher priority. Selecting a route with a higher preference value would mean trusting a less reliable protocol over a more reliable one, which is the opposite of Junos behavior. The route with the higher preference (e.g., OSPF at 10) is only used if the lower-preference route disappears.
- ✗
The OSPF route, because OSPF is a dynamic routing protocol.
Why it's wrong here
Protocol type alone does not determine route selection; Junos assigns a default preference to each protocol based on its trustworthiness and administrative control. OSPF is dynamic, but its internal routes carry a preference of 10, which is higher than the static route's 5. Being dynamic does not auto-prioritize a route; in fact, static routes are often deliberately given a lower preference so operators can precisely control routing decisions.
- ✓
The static route, because it has a lower preference value.
Why this is correct
Junos routes are selected by comparing the preference values from different protocols, and the route with the lowest preference is installed as active in the forwarding table. Static routes have a default preference of 5, while OSPF internal routes use 10, so the static route is chosen. This lower preference value reflects that static routes are manually configured and therefore considered the most reliable and predictable source for that destination.
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
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