Important Juniper JN0-106 JNCIA-Junos Exam Questions

Answer: B, D

Explanation:

Route preference is the quantitative value Junos OS uses to rank the trustworthiness of different routing sources when multiple protocols provide a path to the same destination. A critical architectural distinction in Junos is that both direct and local routes share the same default preference value of 0. Direct routes represent subnets physically connected to an interface, while local routes represent the specific IP address assigned to the device interface itself. Because a value of 0 is the lowest possible numerical value, these routes are always preferred over any learned via dynamic protocols or static configuration.

Additionally, Junos OS treats External BGP (EBGP) and Internal BGP (IBGP) differently than other vendors by assigning both an identical default preference of 170. This means that if the same prefix is learned via both EBGP and IBGP, the preference value alone will not determine the active route; the system must instead proceed to the standard BGP path selection algorithm (evaluating attributes like Local Preference, AS Path, and Origin) to break the tie. In contrast, OSPF distinguishes between its route types, assigning a preference of 10 to internal routes and 150 to AS external routes. Understanding these default values---specifically the parity between direct/local and the unified preference for BGP variants---is foundational for predicting how the Routing Engine populates the forwarding table. Reference: Routing Fundamentals, Default Route Preference Values.

Answer: A

Explanation:

Analyzing the provided exhibit of the inet.0 routing table reveals that the destination network 10.0.0.0/24 currently has two viable paths: a static route with a preference of 5 and an OSPF route with a preference of 10. Both routes are configured to use 10.12.0.1 via the ge-0/0/1.0 interface as their primary next hop. The static route is currently marked with an asterisk (*), indicating it is the active path chosen by the Routing Engine due to its lower preference value.

In the event that the ge-0/0/1 interface transitions to a 'down' state, the physical layer failure triggers the immediate invalidation of all routes associated with that link. Consequently, both the specific static and OSPF routes for the 10.0.0.0/24 prefix are purged from the active forwarding table. The Routing Engine must then perform a re-evaluation of the routing table to identify the next best match for any traffic destined for that range. Since there are no other more specific or equally specific routes available for the 10.0.0.0/24 network, the router falls back to the default route (0.0.0.0/0). As shown in the exhibit, the default route points to the next-hop address 10.23.0.3 via interface ge-0/0/2.0. Therefore, if the primary interface fails, traffic will be redirected through this secondary gateway.

Answer: D

Explanation:

Securing the management plane is a core requirement for any Junos OS deployment. Secure Shell (SSH) is the industry-standard protocol used to provide encrypted, authenticated remote access to the Junos Command Line Interface (CLI). Unlike Telnet, which transmits both administrative credentials and command data in cleartext, SSH utilizes public-key cryptography to establish a secure tunnel, protecting the session from eavesdropping, man-in-the-middle attacks, and unauthorized interception.

In Junos OS, SSH is typically enabled within the [edit system services] hierarchy. Once active, it allows administrators to perform operational and configuration tasks with the assurance that their management traffic remains confidential. Beyond simple terminal access, SSH serves as the transport mechanism for other secure management functions, such as the NETCONF XML management protocol and Secure Copy (SCP) for file transfers. For high-security environments, Junos supports advanced SSH features including key-based authentication, strong cipher suites, and multi-factor authentication integration. Disabling insecure protocols like Telnet and FTP in favor of SSH and SFTP/SCP is a foundational best practice for hardening the Routing Engine against external threats.

Answer: B

Explanation:

The load command in Junos OS provides several operational methods for importing configuration data into the candidate buffer. When an administrator needs to perform a 'clean slate' update---where the objective is to completely replace the existing candidate configuration with a new hierarchical file---the override option is the correct tool. Unlike load merge, which blends new data with the existing configuration, or load replace, which only updates specifically tagged sections, load override discards every statement currently in the candidate configuration and substitutes it entirely with the new content.

Using the terminal keyword in conjunction with override allows the architect to paste a large hierarchical configuration directly into the Command Line Interface (CLI). This is the most efficient method for applying validated templates, restoring full system backups, or migrating configurations between devices without having to manually delete existing parameters. After the data is pasted and the process is finalized (typically with a Ctrl+D sequence), the Junos OS kernel validates the new candidate configuration against the device's hardware and software capabilities. To make these changes active and operational, a subsequent commit command must be executed. This comprehensive replacement mechanism ensures configuration integrity by eliminating any potential remnants of previous, unwanted settings that might conflict with the new deployment.

Answer: C

Explanation:

In the Junos OS architecture, maintaining a reliable recovery point is a critical post-installation task. While the system automatically archives previous configurations as 'rollback' files every time a commit is performed, these files are transient and can eventually be rotated out of the default 50-file history as new changes are made. To ensure a permanent and reliable recovery state, a Senior Architect should manually create a rescue configuration.

The rescue configuration is a specifically designated file used to restore a device to a known-working state if it becomes unreachable or the configuration becomes corrupted. Unlike standard rollbacks, the rescue configuration is only created or updated when an administrator explicitly issues the operational mode command request system configuration rescue save. This ensures that even if several subsequent commits flush the desired initial state from the standard rollback archive, the 'safe harbor' configuration remains intact on the storage media. This state can then be re-activated via the rollback rescue command in configuration mode followed by a commit. Setting a rescue configuration after the initial setup is a foundational best practice for disaster recovery and operational stability, providing a 'last resort' configuration that is immune to the automated rotation of the commit history.