The JN0-106 exam validates your foundational knowledge of Juniper routing and switching technologies within the Junos, Associate (OS 21.2) certification track. This exam is designed for network professionals who support service provider environments and need to demonstrate competency across core Juniper platform concepts. This landing page outlines the exam syllabus, question formats, and practical preparation strategies to help you study efficiently and build confidence before test day.
Use this topic map to guide your study for Juniper JN0-106 (Junos, Associate (OS 21.2)) within the Juniper Service Provider Routing & Switching Certification path.
The JN0-106 exam uses multiple-choice and scenario-based questions to assess both theoretical knowledge and practical decision-making ability. Questions progress in difficulty and reflect real-world situations you would encounter in a service provider network.
Questions are designed to reward both breadth of knowledge and depth of hands-on experience, so practice with real Junos systems or simulators whenever possible.
An effective study plan breaks the syllabus into weekly goals, combines passive learning with active practice, and includes timed mock exams to build test-day confidence. Aim for 4-6 weeks of consistent study, allocating more time to topics that are new or challenging for you.
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Junos OS Fundamentals, Configuration Basics, and Routing Fundamentals typically account for a larger portion of the exam. However, all seven topics are tested, so balanced preparation across all areas is important. Review the official exam blueprint to confirm the exact weighting for your test date.
Networking Fundamentals provides the foundation for understanding how data moves. Junos OS Fundamentals and User Interfaces teach you how to work with the platform. Configuration Basics and Operational Monitoring and Maintenance cover day-to-day tasks. Routing Fundamentals and Routing Policy and Firewall Filters determine how traffic is forwarded and controlled. In practice, you use all of these together: you configure a routing policy (topic 7) based on network requirements (topic 1), verify it with show commands (topic 5), and troubleshoot issues using CLI skills (topic 3).
Hands-on experience significantly improves exam performance and real-world competency. Prioritize labs that cover Configuration Basics (building interfaces and routes) and Operational Monitoring and Maintenance (using show commands and interpreting output). If possible, also practice Routing Policy and Firewall Filters in a lab environment. Even 2-3 hours per week on a simulator or test device will reinforce muscle memory and build confidence.
Many candidates struggle with CLI syntax details, confuse similar protocols or features, or misinterpret show command output. Others skip the explanation step when reviewing practice questions, so they repeat the same mistakes on the real exam. Avoid these pitfalls by typing commands in a lab, not just reading them, and by always understanding why an answer is correct, not just memorizing it.
Focus on review and reinforcement rather than learning new material. Spend 30-45 minutes daily reviewing your weakest topics, redo challenging practice questions, and take one full-length timed mock exam. Get adequate sleep in the days leading up to the test, and on exam day, read each question carefully, flag uncertain items for review, and manage your time to answer all questions.
What is the main function of the forwarding table on a Junos device?
The architecture of Junos OS is designed with a strict functional separation between the control plane and the data plane. The Routing Engine (RE) maintains the master Routing Information Base (RIB), which acts as a comprehensive database storing all potential paths learned from various routing protocols, static configurations, and direct connections. However, to achieve wire-speed performance, the device does not consult the RIB for every packet. Instead, the RE identifies the 'active' or best routes for each destination based on route preference and metrics.
Once these active routes are selected, the RE distills them into a streamlined Forwarding Information Base (FIB), commonly referred to as the forwarding table, and pushes this table to the Packet Forwarding Engine (PFE). The main function of the forwarding table is to provide a high-speed, local lookup mechanism that allows the PFE to forward transit traffic across the switch fabric with minimal latency. This table contains only the specific exit interface and Layer 2 next-hop information required for packet delivery. By isolating the PFE from the overhead of complex routing protocol state machines and all inactive redundant paths, Junos OS ensures that forwarding performance remains consistent even during control plane re-convergence. Reference: Junos OS Fundamentals, Control Plane and Forwarding Plane functions.
Refer to the exhibit.
Referring to the exhibit, which two statements about IPv6 routing are correct? (Choose two.)
The provided exhibit displays the output of the show route table inet6.0 command, which represents the master routing table for IPv6 unicast traffic in Junos OS. Analysis of the specific route entries reveals that all listed destinations are categorized as either [Direct/0] or [Local/0]. These route types indicate that the table only contains networks physically connected to the router's interfaces and the specific IP addresses assigned to those interfaces.
Because there are no routes identified by dynamic protocols (such as OSPFv3, IS-IS, or BGP) or static entries, it is verified that the router is not learning IPv6 routes from any neighbors or peers. Consequently, the routing table lacks reachability information for any non-local or remote IPv6 segments. Without these routes or a configured default gateway (::/0), the router is unable to forward traffic to remote IPv6 networks. Statements C and D are factually incorrect based on the exhibit: the 2001:db8:22:108::/64 network is associated with interface ge-0/0/4.0 (not ge-0/0/5.0), and the 2001:db8:22:107::/64 network is entirely absent from the displayed routing table.
Which protocol is used to discover the Layer 2 (MAC) address of a next hop for IPv6 hosts?
In the IPv6 protocol suite, the traditional Address Resolution Protocol (ARP) used in IPv4 has been deprecated and replaced by the Neighbor Discovery Protocol (NDP). NDP is a multifaceted protocol built upon the Internet Control Message Protocol version 6 (ICMPv6). Its primary purpose is to allow a host or router to determine the Layer 2 hardware (MAC) address of a neighbor on the same local link when only the neighbor's IPv6 address is known.
This specific process is known as Neighbor Solicitation and Neighbor Advertisement. When a Junos device needs to resolve a MAC address for an IPv6 next hop, it sends a Neighbor Solicitation (ICMPv6 Type 135) message to the solicited-node multicast address. The target host responds with a Neighbor Advertisement (ICMPv6 Type 136) containing its physical MAC address. Beyond address resolution, NDP also handles Router Discovery, Prefix Discovery, and Duplicate Address Detection (DAD). Unlike ARP, which relies on broadcasts that can impact all hosts on a segment, NDP utilizes efficient multicast communication. Understanding NDP is critical for Junos architects, as it is the foundational mechanism that facilitates logical-to-physical address mapping in modern IPv6 environments, ensuring that the Packet Forwarding Engine can properly encapsulate frames for local delivery.
Click the Exhibit button.
How is traffic, sourced from 10.0.0.0/8, treated by the firewall filter shown in the exhibit?
Junos OS firewall filters operate on a sequential, 'first-match' logic, but their behavior is significantly influenced by the use of terminating versus non-terminating actions. In this exhibit, a packet with a source address of 10.0.0.0/8 is evaluated against the filter named test.
Evaluation begins with term 1. The packet matches the source-address criteria, triggering the actions defined in the then statement. The first action is log, which sends the packet header information to the firewall task buffer for logging. The second action is next term. This is a critical non-terminating action; it instructs the Packet Forwarding Engine (PFE) to continue the evaluation process using the subsequent term in the filter rather than stopping after the match.
Evaluation then moves to term 2. Because term 2 contains no from match conditions, it acts as a 'catch-all' for any traffic that reaches it. The action in this term is reject. This is a terminating action that discards the packet and sends an ICMP 'destination unreachable' message back to the source. Therefore, the packet is first recorded by the logging process and is subsequently dropped by the rejection mechanism. If next term had not been present in term 1, the packet would have been implicitly accepted (as any matched term without a terminating action like discard, reject, or accept defaults to an implicit accept in that specific term). However, the explicit instruction to move forward ensures the packet hits the reject statement.
You successfully committed a configuration change. You now realize an issue exists and must revert back to the previous configuration. Which command entered in configuration mode will accomplish this task when committed?
Junos OS features a sophisticated configuration management system that automatically creates a snapshot of the active configuration every time a commit is successfully performed. These snapshots are stored as rollback files in a historical archive. Within the configuration mode hierarchy, the rollback command allows an administrator to discard current candidate changes and load a previously committed configuration into the candidate buffer.
The numbering of these rollback files is sequential and follows a specific logic: rollback 0 represents the configuration that is currently active and running on the system. To revert to the state that existed immediately prior to the most recent commit, the administrator must use rollback 1. This command overwrites the current candidate configuration with the previous operational state. It is important to note that executing rollback 1 does not immediately impact the running system; it merely populates the candidate database. The changes must still be verified---often using show | compare---and then finalized by executing the commit command. By default, Junos maintains up to 50 of these rollback configurations (and up to 100 on certain platforms/versions), providing a robust safety net for operational recovery and auditing. Reference: Configuration Basics, Managing Configurations, Rollback configurations.
