Visit here for our full Juniper JN0-105 exam dumps and practice test questions.

Question 106

Which Junos command is used to display the current routing table on a Juniper device?

A) show route table

B) show routing-table

C) show ip route

D) show route

Answer: D

Explanation:

The correct command to display the current routing table on a Juniper device running Junos OS is show route. This fundamental command provides comprehensive information about all routes known to the device, including their destination prefixes, next-hop addresses, preferences, and the protocols that installed them into the routing table.

When executed, the show route command displays routes from all routing tables by default, with the inet.0 table being the primary IPv4 unicast routing table. The output includes critical information such as destination networks, active and inactive routes, next-hop gateway addresses, route preferences, protocol origins, and age of each route entry. Understanding this command is essential for network troubleshooting and verification tasks.

The command can be enhanced with various options and filters to narrow down results. For example, show route protocol ospf displays only OSPF routes, show route 192.168.1.0/24 shows routes for a specific prefix, and show route extensive provides detailed information including route attributes and communities. These filtering capabilities make the command extremely versatile for different troubleshooting scenarios.

The option show route table is incorrect because while table is a valid keyword for specifying routing table instances, the base command structure is show route followed by optional parameters. The command show routing-table does not exist in Junos syntax and represents incorrect command structure. The command show ip route is Cisco IOS syntax and will not function on Juniper devices, which use completely different command structures.

Junos uses a hierarchical command structure that differs significantly from other network operating systems. The show route command is part of the operational mode command set, which allows viewing and monitoring but not configuration changes. Mastering this command and its various options is crucial for anyone working with Juniper networks as it forms the foundation for understanding how traffic is forwarded through the network and troubleshooting routing issues effectively.

Question 107

What is the default root password behavior when initially accessing a Juniper device?

A) The default password is admin123

B) No root password is set by default

C) The default password is juniper

D) A random password is generated and displayed on console

Answer: B

Explanation:

When initially accessing a Juniper device running Junos OS, no root password is set by default. This means that when you first connect to a new or factory-reset Juniper device through the console port, you can log in as root without being prompted for a password. This design allows administrators immediate access to configure the device during initial setup.

The absence of a default password is a deliberate security design that requires administrators to set a root password during the initial configuration process. Junos will not allow you to commit a configuration without first setting a root password, enforcing basic security practices from the start. This approach ensures that devices cannot be deployed into production without proper authentication being configured.

During initial configuration, administrators typically enter configuration mode using the configure command, then set the root password using the command set system root-authentication plain-text-password. The system will prompt you to enter and confirm the password. Alternatively, you can use encrypted passwords or SSH keys for authentication. Once the password is set and the configuration is committed, all future logins will require this password.

The option stating the default password is admin123 is incorrect as Juniper devices do not ship with this or any preset password. Similarly, juniper is not a default password, though this is a common misconception. Some vendors use default passwords, but Juniper takes a different approach by requiring password creation during initial setup. The option about a random generated password is also incorrect as no automatic password generation occurs on Juniper devices.

Understanding this default behavior is critical for initial device setup and security planning. Organizations should have documented procedures for setting strong root passwords and should change these passwords regularly according to security policies. The root account has complete administrative privileges, so protecting it with a strong password and potentially additional authentication methods like SSH keys is essential for maintaining device security.

Question 108

Which Junos configuration mode command is used to save configuration changes permanently?

A) save configuration

B) write memory

C) commit

D) apply changes

Answer: C

Explanation:

The commit command is used in Junos configuration mode to save configuration changes permanently and make them active on the device. This command is fundamental to the Junos configuration model and represents one of the key differences between Junos and other network operating systems. Understanding the commit process is essential for anyone working with Juniper devices.

When you enter configuration mode and make changes, those changes are stored in a candidate configuration that exists separately from the active configuration currently running on the device. The changes you make do not affect device operation until you execute the commit command. This separation provides a safety mechanism that allows you to prepare complex configuration changes, review them, and then activate them all at once.

The commit process includes several stages including syntax checking where Junos validates that all commands follow proper syntax rules, semantic checking where the system verifies that configuration statements make logical sense and reference valid objects, dependency checking where relationships between configuration elements are verified, and activation where if all checks pass the candidate configuration replaces the active configuration. If any errors are detected, the commit fails and the active configuration remains unchanged.

Junos offers several commit options that enhance flexibility and safety including commit confirmed which automatically rolls back changes after a specified time unless confirmed, commit check which validates configuration without activating it, commit and-quit which commits changes and exits configuration mode, and commit comment which adds descriptive text to the commit for logging purposes. These options provide powerful tools for safe configuration management.

The command save configuration does not exist in Junos syntax. The command write memory is Cisco IOS syntax used to save running configuration to startup configuration and will not work on Juniper devices. The command apply changes is not valid Junos syntax. Only commit properly saves and activates configuration changes in Junos OS.

Question 109

What is the purpose of the pipe symbol in Junos operational mode commands?

A) To execute multiple commands simultaneously

B) To filter or modify command output

C) To redirect output to a file only

D) To create command aliases

Answer: B

Explanation:

The pipe symbol in Junos operational mode commands is used to filter or modify command output, providing powerful tools for managing and analyzing large amounts of information returned by show commands. This functionality allows administrators to quickly find specific information within extensive command outputs, making troubleshooting and verification tasks much more efficient.

The pipe functionality in Junos works by taking the output from a command and passing it through various filters or processing tools. Common pipe operations include match which displays only lines containing a specified string, except which displays lines that do not contain a specified string, find which starts displaying output from the first line matching the pattern, count which displays the number of lines in the output, and last which displays the end of the output with optional line count specification.

Practical examples demonstrate the power of pipe operations. The command show configuration displays the entire configuration and show configuration | match ospf shows only configuration lines containing ospf. Similarly, show route | except Static displays all routes except static routes and show interfaces terse | count shows the number of output lines which effectively counts interfaces. These filtering capabilities are invaluable when working with complex configurations or large routing tables.

Advanced pipe operations can be chained together for more sophisticated filtering. For example, show log messages | match error | except kernel | last 20 would display the last 20 log entries containing error but excluding those with kernel. This multi-stage filtering allows precise extraction of relevant information from voluminous outputs.

The pipe symbol does not execute multiple commands simultaneously as Junos processes commands sequentially. While output can be redirected to files using different syntax, the pipe symbol primary purpose is filtering and modifying output display rather than file redirection. Creating command aliases uses different Junos features and is not accomplished through pipe operations. Understanding pipe functionality significantly enhances operational efficiency when working with Juniper devices.

Question 110

Which routing protocol uses Dijkstra’s algorithm to calculate the shortest path?

A) RIP

B) BGP

C) OSPF

D) Static routing

Answer: C

Explanation:

OSPF uses Dijkstra’s algorithm, also known as the Shortest Path First algorithm, to calculate the best path to destination networks. This link-state routing protocol builds a complete topology map of the network and uses this mathematical algorithm to determine the optimal route based on cumulative link costs from source to destination.

The OSPF process using Dijkstra’s algorithm involves several steps. First, each router discovers its neighbors and establishes adjacencies through hello packets. Then routers exchange link-state advertisements containing information about their connected links, costs, and states. Each router builds an identical link-state database containing the complete network topology. Finally, each router runs Dijkstra’s algorithm independently using itself as the root to calculate the shortest path tree to all destinations.

Dijkstra’s algorithm works by systematically examining paths and selecting the one with the lowest cumulative cost. The algorithm maintains a set of visited nodes and iteratively selects the unvisited node with the lowest cost from the source, adds it to the visited set, and updates costs to its neighbors. This process continues until all reachable nodes have been processed, resulting in a shortest path tree that forms the basis for the routing table.

The advantage of using Dijkstra’s algorithm in OSPF includes guaranteed shortest path calculation based on configured metrics, fast convergence when topology changes occur, loop-free routing because each router has complete topology knowledge, and scalability through hierarchical design using areas. These characteristics make OSPF suitable for large enterprise and service provider networks.

RIP uses the Bellman-Ford algorithm and makes routing decisions based on hop count rather than link-state information. BGP is a path-vector protocol that uses best path selection based on multiple attributes rather than Dijkstra’s algorithm. Static routing does not use any algorithm as routes are manually configured by administrators. Only OSPF among these options employs Dijkstra’s algorithm for route calculation.

Question 111

What is the primary function of the Junos kernel layer?

A) Provide user interface for configuration

B) Handle packet forwarding and system operations

C) Store configuration files

D) Generate routing protocol advertisements

Answer: B

Explanation:

The Junos kernel layer serves as the core operating system foundation that handles packet forwarding, system operations, and hardware management. Based on FreeBSD, the kernel provides essential low-level functions that enable the device to process traffic, manage resources, and coordinate between hardware and software components.

The kernel’s primary responsibilities include managing the forwarding plane where packet forwarding decisions are executed at high speed, controlling hardware interfaces including physical ports and internal components, allocating system resources such as memory and CPU cycles, providing inter-process communication between various Junos daemons, and implementing core networking protocols at the operating system level. These functions form the foundation upon which all other Junos components operate.

In the Junos architecture, there is clear separation between control plane and forwarding plane functions. The kernel works closely with the Packet Forwarding Engine which handles actual packet forwarding at wire speed using specialized hardware. The kernel manages communication between the control plane running routing protocols and management functions and the forwarding plane executing packet forwarding. This separation allows for high performance and stability.

The kernel also provides stability and reliability features including process isolation where different system functions run as separate processes, crash protection where one process failure does not bring down the entire system, memory protection preventing processes from interfering with each other, and system recovery mechanisms that restart failed processes automatically. These architectural features contribute to Junos reputation for stability and reliability.

Providing user interface for configuration is handled by higher-level management processes and the CLI daemon, not the kernel itself. Storing configuration files is performed by the management daemon and file system, not a kernel function. Generating routing protocol advertisements is the responsibility of routing protocol daemons that run on top of the kernel. The kernel provides the foundation but these specific functions are implemented by other Junos components.

Question 112

Which file contains the active configuration currently running on a Junos device?

A)conf

B)conf.gz

C)conf

D) rollback configuration files

Answer: B

Explanation:

The juniper.conf.gz file contains the active configuration currently running on a Junos device. This compressed configuration file represents the configuration that was last successfully committed and is actively controlling device behavior. Understanding the various configuration files and their purposes is essential for effective Junos device management.

The juniper.conf.gz file is stored in the device file system and is automatically updated each time a configuration is successfully committed. The .gz extension indicates the file is compressed using gzip to save storage space. When you execute commands like show configuration, the system reads from this active configuration file. This file persists across reboots, ensuring configuration consistency.

Junos maintains multiple configuration files for different purposes. The candidate configuration is the temporary configuration being edited in configuration mode but not yet committed. Rollback files numbered 0 through 49 contain historical configurations with rollback 0 being the most recent and higher numbers being progressively older. The rescue configuration is a special saved configuration that can be used for recovery purposes when created explicitly by an administrator.

The configuration file system provides powerful capabilities for configuration management. Administrators can compare configurations using commands like show system rollback compare, restore previous configurations using rollback commands, save specific configurations for future reference, and export configurations for backup or documentation purposes. This flexibility supports both routine operations and disaster recovery scenarios.

The file candidate.conf does not exist as a separate file as the candidate configuration exists in memory during configuration mode. The rescue.conf file contains a specially saved configuration for emergency recovery but not the currently active configuration. Rollback configuration files contain historical configurations, not the current active one. Only juniper.conf.gz represents the actual running configuration on the device.

Question 113

What is the default preference value for direct routes in Junos?

A) 0

B) 5

C) 10

D) 20

Answer: A

Explanation:

The default preference value for direct routes in Junos is 0, making them the most preferred route type in the routing table. Direct routes, also known as connected routes, represent networks that are directly attached to the device’s interfaces. The preference value of 0 ensures these routes are always chosen over routes learned through any routing protocol when multiple routes exist to the same destination.

Route preference in Junos, also called administrative distance in other systems, determines which route is installed in the forwarding table when multiple routes to the same destination are available from different sources. Lower preference values indicate more trusted or preferred routes. Since direct routes represent physically connected networks, they receive the lowest possible preference value to ensure local connectivity always takes precedence.

Understanding the default preference hierarchy in Junos is crucial for troubleshooting routing issues. The default preferences are direct routes at 0, static routes at 5, OSPF internal routes at 10, IS-IS Level 1 internal routes at 15, IS-IS Level 2 internal routes at 18, RIP at 100, and BGP at 170. This hierarchy ensures predictable route selection when multiple routing information sources are present.

Administrators can modify preference values to influence route selection, but changing direct route preference is rarely done as it could disrupt fundamental connectivity. More commonly, static route preferences are adjusted to create backup routes or routing protocol preferences are modified to prefer one protocol over another. These modifications use the preference statement in the routing protocol or static route configuration.

The preference value of 5 is the default for static routes, not direct routes. The value 10 is the default for OSPF internal routes. The value 20 is not a default preference for any standard routing protocol in Junos. Only 0 correctly represents the preference for direct routes, reflecting their fundamental importance in the routing hierarchy.

Question 114

Which command displays the Junos software version running on the device?

A) show system version

B) show version

C) show software

D) show junos version

Answer: B

Explanation:

The show version command displays comprehensive information about the Junos software version running on the device, including the specific release number, build date, hostname, device model, and other system identification details. This command is one of the most frequently used operational commands and is essential for system verification and troubleshooting.

The output from show version provides critical information including the Junos OS version number in format like 20.4R3.8, the hostname configured on the device, the device model and hardware platform, the kernel version based on FreeBSD, the build date indicating when this software version was compiled, and copyright information from Juniper Networks. This comprehensive information helps administrators verify correct software installation and identify system characteristics.

Understanding version information is important for several operational tasks. When troubleshooting issues, knowing the exact software version helps determine if known bugs affect your deployment and whether software upgrades might resolve problems. When planning upgrades, you need to know the current version to determine the upgrade path and compatibility. When engaging technical support, version information is typically the first thing requested to provide appropriate assistance.

The Junos versioning scheme follows a specific format that conveys meaningful information. For example, in version 20.4R3.8, the 20 represents the year of initial release, 4 indicates the quarter, R denotes a standard release, 3 is the major maintenance release number, and 8 is the minor build number. Understanding this scheme helps administrators assess version currency and stability characteristics.

The command show system version does not exist in Junos syntax. The command show software is not valid Junos syntax and will not produce output. The command show junos version is also incorrect as Junos does not use this command structure. Only show version is the correct operational command to display software version information on Juniper devices.

Question 115

What is the purpose of the commit confirmed command in Junos?

A) To commit configuration without checking for errors

B) To automatically rollback configuration if not confirmed within a specified time

C) To commit configuration to multiple devices simultaneously

D) To create a backup before committing

Answer: B

Explanation:

The commit confirmed command provides a safety mechanism that automatically rolls back configuration changes if they are not explicitly confirmed within a specified time period. This feature is invaluable for preventing loss of connectivity when making potentially disruptive configuration changes, especially when working on remote devices where configuration errors could lock you out.

When you execute commit confirmed, you can specify a timeout period in minutes with the default being 10 minutes. The configuration changes are activated immediately, but a timer starts counting down. If you do not execute a commit command or commit confirmed again before the timer expires, the system automatically rolls back to the previous configuration. This ensures that if your changes break connectivity and prevent you from accessing the device, it will automatically recover.

The typical workflow using commit confirmed involves preparing configuration changes in configuration mode, executing commit confirmed with an appropriate timeout such as commit confirmed 5 for a five-minute window, testing connectivity and functionality to verify changes work correctly, and executing commit before the timeout expires if everything works properly to make changes permanent. If issues occur and you lose access, simply waiting for the timeout will restore the previous working configuration.

This feature is particularly valuable in several scenarios including making routing protocol changes that could affect reachability, modifying firewall rules that might block management access, changing interface configurations on remote devices, reconfiguring authentication systems, and implementing any changes where there is risk of losing device access. The automatic rollback provides confidence to make necessary changes while maintaining a recovery path.

The commit confirmed command does perform full error checking just like a regular commit, so the option about committing without error checking is incorrect. This command operates on a single device and is not related to multi-device configuration management. While configuration history is maintained, commit confirmed does not explicitly create backups beyond the normal rollback files. Only the automatic rollback functionality correctly describes the purpose of this command.

Question 116

Which Junos configuration hierarchy contains interface-specific settings?

A) [edit system]

B) [edit interfaces]

C) [edit protocols]

D) [edit routing-options]

Answer: B

Explanation:

The [edit interfaces] configuration hierarchy contains all interface-specific settings in Junos, including physical and logical interface configurations, addressing, encapsulation, and interface-level protocol parameters. This hierarchy is fundamental to device configuration as interfaces provide the connection points for network traffic.

Within the interfaces hierarchy, configuration is organized by interface type and unit numbers. Physical interface settings are configured at the interface level such as ge-0/0/0 for a Gigabit Ethernet interface, where settings include MTU, link speed, duplex mode, description, and physical layer parameters. Logical interfaces called units are configured beneath physical interfaces and contain protocol-specific settings like IP addresses, VLAN tags, and encapsulation types.

Common configuration tasks within the interfaces hierarchy include assigning IP addresses using address statements, configuring VLAN tagging with vlan-tagging and vlan-id statements, setting interface descriptions for documentation purposes, defining interface families such as inet for IPv4 or inet6 for IPv6, configuring redundancy features like aggregated Ethernet, and enabling or disabling interfaces administratively. These configurations directly control how interfaces operate and participate in network communication.

The interfaces hierarchy supports various interface types including physical interfaces like ge, xe, and et for different Ethernet speeds, logical interfaces like lo0 for loopback, tunnel interfaces such as gr, ip, and st for various tunneling protocols, virtual interfaces like irb for integrated routing and bridging, and aggregated interfaces like ae for link aggregation. Each interface type has specific configuration options appropriate to its function.

The [edit system] hierarchy contains system-wide settings like hostname, name servers, and authentication, not interface-specific configurations. The [edit protocols] hierarchy configures routing protocols like OSPF and BGP, which reference interfaces but are not where interface settings are configured. The [edit routing-options] hierarchy contains routing policy and routing table settings, not interface configurations. Only [edit interfaces] is the correct location for interface-specific settings.

Question 117

What does the term “commit synchronize” accomplish in a Junos chassis cluster?

A) Synchronizes time between devices

B) Commits configuration to both chassis cluster nodes simultaneously

C) Synchronizes routing tables

D) Backs up configuration to an external server

Answer: B

Explanation:

The commit synchronize command in a Junos chassis cluster commits configuration changes to both chassis cluster nodes simultaneously, ensuring configuration consistency across the high-availability pair. This feature is essential for maintaining synchronized configurations in clustered environments where two devices operate as a single logical unit.

In a chassis cluster configuration, two separate physical devices are configured to work together as a single logical system for high availability purposes. One device serves as the primary node while the other serves as the secondary backup node. Configuration changes are typically made on the primary node, but for proper failover operation, both nodes must maintain identical configurations. The commit synchronize command automates this synchronization process.

When commit synchronize is executed, several actions occur. First, the configuration is validated on the primary node to ensure correctness. Then, the configuration is committed and activated on the primary node. Next, the configuration is automatically transferred to the secondary node over the cluster control link. Finally, the configuration is committed and activated on the secondary node. If any errors occur during this process, the entire commit operation fails, preventing configuration inconsistency.

Using commit synchronize provides several advantages including guaranteed configuration consistency between cluster members, simplified operational procedures as administrators only configure once, reduced risk of configuration drift between nodes, proper preparation for failover scenarios, and audit trail showing synchronized commits. These benefits make commit synchronize the preferred method for configuration changes in chassis cluster environments.

Synchronizing time between devices is accomplished through NTP configuration in the system hierarchy, not through commit synchronize. Routing tables are synchronized through routing protocol operations and kernel processes, not configuration commits. Backing up configuration to external servers uses different commands like save or file copy operations. Only the simultaneous commit to both cluster nodes correctly describes commit synchronize functionality.

Question 118

Which protocol is used by default for device management connections in Junos?

A) Telnet

B) SSH

C) HTTP

D) SNMP

Answer: B

Explanation:

SSH is the default protocol enabled for device management connections in Junos, providing secure encrypted communication for command-line interface access. This default configuration reflects modern security best practices by ensuring that management traffic is protected from eavesdropping and tampering from the moment the device is initially configured.

SSH operates on TCP port 22 and provides several security features including strong encryption of all transmitted data protecting credentials and commands from interception, server authentication through host keys verifying you are connecting to the intended device, client authentication supporting both password and public key methods, and session integrity ensuring data is not modified in transit. These features make SSH far superior to older protocols like Telnet for management access.

Junos SSH configuration resides in the [edit system services] hierarchy. By default, SSH is enabled with protocol version 2 which is the current secure standard. Administrators can customize SSH behavior including restricting connections to specific IP addresses or networks using firewall filters, configuring public key authentication for enhanced security, adjusting connection parameters like timeouts and maximum sessions, and controlling which protocol versions are accepted.

Security best practices for SSH management include disabling root login over SSH by configuring deny-root-login, implementing public key authentication instead of passwords, applying firewall filters to restrict SSH access to authorized management networks, changing the default SSH port if additional obscurity is desired, and regularly reviewing SSH logs for unauthorized access attempts. These practices significantly enhance management security.

Telnet is an insecure clear-text protocol that must be explicitly enabled and should not be used in production environments. HTTP provides web-based management through J-Web but is not the default CLI access method and should be secured with HTTPS. SNMP is used for monitoring and management but is not an interactive CLI protocol. Only SSH provides the secure default management access in Junos.

Question 119

What is the purpose of the “request system snapshot” command in Junos?

A) To capture a screenshot of the current CLI session

B) To back up the current active configuration to a file

C) To create a backup copy of system software partitions

D) To take a snapshot of the routing table

Answer: C

Explanation:

The request system snapshot command creates a backup copy of the primary system software partition to the backup partition on the device storage media. This command is crucial for system recovery and software upgrade procedures as it provides a known good software installation that can be used if the primary partition becomes corrupted or if a software upgrade causes problems.

Juniper devices use a dual-partition storage architecture where system software can be installed on either a primary or backup partition. The snapshot command copies the currently running software from whichever partition is active to the alternate partition. This ensures that if you upgrade software on one partition and encounter issues, you can reboot from the other partition which contains the previous working version.

The snapshot process involves several steps. The command validates that sufficient storage space exists on the target partition, copies all necessary system files including the kernel and file system from the active partition to the backup partition, updates partition information so the system knows both partitions contain valid software, and completes with a confirmation message. The entire process typically takes several minutes depending on device model and storage speed.

Best practices recommend creating a snapshot in several scenarios including before performing software upgrades to preserve the current working version, after successfully upgrading and validating a new software version to protect it, as part of regular maintenance procedures to ensure backup partition currency, and before making major configuration changes that might affect system stability. Having a current snapshot significantly reduces recovery time if problems occur.

The command does not capture screenshots of CLI sessions as Junos is command-line based without graphical screenshot capability. Backing up active configuration uses different commands like show configuration or request support information. Taking snapshots of routing tables would use commands like show route. Only creating backup copies of system software partitions correctly describes request system snapshot functionality.

Question 120

Which Junos feature allows administrators to view and roll back to previous configurations?

A) Configuration snapshots

B) Configuration rollback

C) Configuration backup

D) Configuration archive

Answer: B

Explanation:

Configuration rollback is the Junos feature that allows administrators to view and roll back to previous configurations, providing powerful configuration management and recovery capabilities. This feature automatically maintains a history of configuration changes, enabling quick recovery from configuration errors or the ability to compare changes over time.

Junos automatically maintains up to 50 previous configurations numbered from 0 to 49, where rollback 0 is the currently active configuration, rollback 1 is the previous configuration, and higher numbers represent progressively older configurations. Each time you successfully commit a configuration, the current configuration becomes rollback 1, rollback 1 becomes rollback 2, and so on. This automatic versioning requires no administrator action and provides a comprehensive change history.

Administrators can use rollback features in several ways. The command show system rollback displays information about available rollback configurations including when they were committed and by whom. The command show configuration rollback n displays the contents of a specific rollback configuration where n is the rollback number. The command rollback n in configuration mode loads a previous configuration into the candidate configuration for review or commitment. The command show compare rollback n m compares two rollback configurations.

Practical use cases for configuration rollback include recovering from configuration mistakes by rolling back to the last working configuration, investigating configuration changes by comparing current and previous versions, auditing who made changes and when by examining rollback history and commit logs, and implementing complex changes by testing configurations and rolling back if issues arise. These capabilities make rollback an essential tool for configuration management.

Configuration snapshots typically refer to system software backups created with request system snapshot, not configuration history. Configuration backup suggests external backup processes rather than the built-in rollback mechanism. Configuration archive is not the standard Junos terminology for this feature. Only configuration rollback accurately describes the feature that maintains automatic configuration history and enables restoration of previous configurations.