JN0-106 Routing Fundamentals Practice Question
A network administrator wants to filter routes from being installed in the routing table based on certain criteria. Which Junos feature should be used?
⚠ Common exam trap
It's easy for candidates to confuse a match condition (like a prefix list or community list) with the actual Junos feature that applies the filter (the routing policy), leading candidates to select a component rather than the complete mechanism.
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
✓
Routing policy (import)
B is correct because a routing policy with an import term is the Junos mechanism to control which routes are accepted into the routing table from a routing protocol or a peer. By defining match conditions (e.g., prefix, community, AS path) and an action (accept or reject), the administrator can filter routes before they are installed. This is the standard Junos approach for route filtering at the routing table level.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Community list
Why it's wrong here
A community list is a match condition used within a routing policy to identify routes carrying specific BGP community values. However, simply configuring a community list has no direct effect on the routing table; it must be embedded in a policy statement with an action such as accept or reject, and that policy must be applied in the import direction. Therefore, a community list is not a standalone route-filtering mechanism—it is a matching tool that only works in combination with a routing policy.
- ✓
Routing policy (import)
Why this is correct
In Junos, the correct way to filter routes from being installed is to apply an import routing policy. An import policy is attached to a routing protocol or BGP group and is evaluated when routes are received; if a route does not match the policy's conditions, it is rejected and not placed into the routing table. This policy can also modify route attributes before installation, giving the administrator fine-grained control over what is learned and used for forwarding.
- ✗
Prefix list
Why it's wrong here
A prefix list is a building block that defines a set of IP prefixes for matching purposes, but it cannot filter routes by itself. It must be referenced inside a routing policy statement as a match condition, and that policy must then be applied in the import direction to actually prevent a route from entering the routing table. Without being tied to a policy action, a prefix list is simply an inert object with no filtering capability.
- ✗
Firewall filter
Why it's wrong here
Firewall filters operate in the data plane, inspecting packet headers and determining whether each packet should be forwarded or dropped. They do not evaluate route advertisements or interact with the routing table's control plane, so they have no ability to prevent a route from being installed. Even if a firewall filter drops all traffic matching a route, the route can still exist in the routing table and be advertised to peers; therefore, it is not a valid tool for route filtering.
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.