JN0-106 Routing Fundamentals Practice Question
An organization has two ISPs and wants to load-balance traffic equally across both links for all outbound traffic. Which routing configuration approach should be used?
⚠ Common exam trap
Test-takers frequently confuse metric (cost) with preference (administrative distance) in Junos, assuming that different metric values still allow load balancing, whereas Junos requires equal metric values for ECMP to activate.
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
✓
Configure two static default routes with equal metric values and enable ECMP.
Configuring two static default routes with equal metric values and enabling Equal-Cost Multi-Path (ECMP) allows the Juniper device to load-balance outbound traffic equally across both ISP links. ECMP uses per-flow or per-packet load balancing based on the hash of source/destination IP addresses and ports, ensuring traffic is distributed evenly without relying on dynamic routing protocols.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Configure two static default routes with different metric values.
Why it's wrong here
Configuring two static default routes with different metric values results in Junos selecting only the route with the lower preference. The higher-metric route remains in the configuration as a backup but is not actively used for forwarding. Consequently, all traffic is sent through one ISP only, so this approach cannot achieve load balancing.
- ✗
Configure policy-based routing to match all traffic and forward to both ISPs.
Why it's wrong here
Policy-based routing matches traffic to a next-hop based on policy, but it cannot split a single flow across two equal-cost paths; it forwards matched traffic to one next-hop per policy term, so it cannot achieve per-packet or per-flow load balancing to both ISPs simultaneously. This option is tempting because policy-based routing is often used to steer specific traffic types to different providers, such as sending voice traffic to one ISP and data to another, which would be correct for selective forwarding rather than equal load sharing.
- ✓
Configure two static default routes with equal metric values and enable ECMP.
Why this is correct
In Junos, two static default routes with equal metrics have the same preference and are both installed in the routing table as equal-cost paths. To actually balance traffic, you must enable ECMP, typically by configuring 'load-balance per-packet' in the forwarding options or a policy statement. This allows Junos to distribute flows across both ISPs while maintaining per-flow consistency, which is essential for TCP sessions.
- ✗
Establish BGP sessions with both ISPs and rely on BGP path selection.
Why it's wrong here
Relying on BGP path selection alone will pick one best path based on attributes such as local-pref, AS path, and MED, and install only that path in the routing table. Unless you explicitly configure BGP multipath (e.g., 'multipath' at the group level), only one next-hop is active. Even with multipath, you must also configure load balancing in the forwarding table; the base configuration provided in the question does not include these extra steps. As stated, this option would not produce load balancing between the two ISPs.
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.