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Question 16
What is the purpose of the commit command in Junos OS?
A) To save configuration changes temporarily
B) To activate configuration changes and make them part of the running configuration
C) To delete the current configuration
D) To display configuration differences
Answer: B
Explanation:
The commit command in Junos OS is used to activate configuration changes and make them part of the active running configuration on the device. When administrators make configuration changes in Junos, those changes are initially stored in a candidate configuration that exists separately from the active running configuration. The commit command validates the candidate configuration and, if valid, activates it as the new running configuration.
This two-stage configuration process provides significant safety benefits compared to systems where changes take effect immediately. Administrators can make multiple related changes, review them comprehensively using commands like show compare, and then activate all changes atomically with a single commit operation. If validation fails during the commit process, Junos reports errors and the running configuration remains unchanged.
The commit process includes several validation steps including syntax checking, semantic validation to ensure configuration consistency, and verification that required statements are present. Junos also maintains a rollback history of previous configurations, allowing administrators to revert changes if needed using the rollback command followed by commit.
Option A is incorrect because the commit command activates changes rather than temporarily saving them; candidate configuration changes are automatically saved as you make them. Option C is wrong as commit activates the candidate configuration rather than deleting configurations. Option D is incorrect because the show compare command displays configuration differences, not the commit command.
Understanding the commit process is fundamental to Junos configuration management and ensures administrators can make changes safely with the ability to validate before activation.
Beyond its core function of activating configuration changes, the commit command in Junos OS supports several optional modifiers that enhance administrative control and safety. For example, administrators can use commit check to perform a full validation of the candidate configuration without actually applying it. This is especially useful in collaborative environments where multiple engineers may be editing the configuration simultaneously and want to ensure correctness before final activation. Another useful option is commit confirmed, which temporarily applies the configuration and requires manual confirmation within a specified time period. If the administrator becomes disconnected or forgets to confirm, Junos automatically rolls back to the previous known-good configuration. This feature provides an additional safeguard during remote maintenance or when making changes that could impact management connectivity.
Junos also supports commit synchronize in dual Routing Engine (RE) systems, ensuring that configuration changes are consistently applied across both engines. This avoids configuration drift and maintains redundancy. Additionally, Junos records detailed commit history, including who made each change and when, which is invaluable for auditing and troubleshooting operational issues.
The overall design of Junos’ commit model emphasizes predictability, safety, and clarity. By separating the candidate and active configurations, Junos allows administrators to stage changes carefully, validate them rigorously, and deploy them reliably. This structured workflow reduces the likelihood of configuration errors, minimizes downtime, and supports stable long-term network operations.
Question 17
Which command displays the current active configuration in Junos OS?
A) show configuration
B) display configuration
C) show running-config
D) get configuration
Answer: A
Explanation:
The show configuration command displays the current active configuration in Junos OS, showing all configuration statements that are currently running on the device. This command can be executed from operational mode and provides a comprehensive view of the device’s configuration including interfaces, protocols, routing policies, security settings, and system parameters.
Administrators can modify the show configuration command with various options to filter or format output. For example, show configuration interfaces displays only interface configuration, show configuration protocols shows routing protocol configuration, and show configuration | display set shows configuration in set command format. These filtering options help administrators focus on specific configuration sections.
The show configuration command can also be used with pipe modifiers to search, filter, or format output. Common operations include using match to find specific configuration statements, except to exclude certain sections, and display inheritance to show inherited configuration values. These capabilities make configuration review and troubleshooting more efficient.
Option B is incorrect because display configuration is not a valid Junos command; display is typically used as a pipe modifier rather than a base command. Option C is wrong as show running-config is Cisco IOS syntax, not Junos; Junos uses show configuration instead. Option D is incorrect because get configuration is not valid Junos syntax for viewing configuration.
Understanding how to view configuration is essential for verifying settings, troubleshooting issues, and documenting device configurations in Junos environments.
In addition to its basic function, the show configuration command supports several advanced features that enhance usability and help administrators interpret complex configurations more efficiently. One such feature is hierarchical navigation. Because Junos OS organizes configuration statements in a structured hierarchy, administrators can specify exact paths, such as show configuration system services or show configuration security policies, to quickly retrieve only the relevant sections. This hierarchical structure is one of the core design strengths of Junos, allowing for clear organization and easier long-term maintenance of device settings.
The command is also useful for identifying configuration inheritance through group definitions. By using show configuration | display inheritance, administrators can clearly see which statements come from system-defined groups or user-created configuration groups, making it easier to understand why certain parameters are applied. This is particularly valuable in environments that rely heavily on standardized templates to ensure consistency across multiple devices.
Another powerful option is show configuration | compare rollback X, which compares the current active configuration with a previous rollback version. This comparison helps administrators quickly identify changes that may have introduced issues. When paired with commit history and rollback features, this capability significantly speeds up troubleshooting and configuration audits.
Administrators working in large-scale or multi-team environments also benefit from the show configuration | display xml option, which outputs the configuration in a machine-readable XML format suitable for automation tools, scripting workflows, or integration with configuration management systems like Ansible or Juniper’s own Junos PyEZ automation framework. By mastering the many forms of the show configuration command, network professionals can efficiently validate changes, document configurations, and maintain a high level of operational reliability across Junos-powered networks.
Question 18
What is the default root password behavior on a new Junos device?
A) The root password is blank and must be set before commit
B) The root password is automatically generated
C) The root password is “juniper”
D) No root password is required
Answer: A
Explanation:
On a new Junos device, the root password is blank by default and must be set before the configuration can be committed. Junos enforces this security requirement to ensure that administrators establish proper authentication before the device becomes operational. When attempting to commit a configuration without setting a root password, Junos displays an error message indicating that the root authentication password must be configured.
Setting the root password is accomplished using the command set system root-authentication plain-text-password in configuration mode. After entering this command, Junos prompts the administrator to enter and confirm the new password. Alternatively, administrators can configure encrypted passwords or SSH keys for root authentication using appropriate configuration statements.
This password requirement is a security feature that prevents devices from being deployed with default or no credentials, which would create significant security vulnerabilities. Best practices recommend setting strong passwords and implementing additional authentication mechanisms such as SSH key-based authentication for enhanced security in production environments.
Option B is incorrect because Junos does not automatically generate a root password; administrators must explicitly set it. Option C is wrong as “juniper” is not set as a default password on new devices; the password field is empty. Option D is incorrect because while the initial password is blank, Junos requires a password to be set before committing configuration.
Understanding root password requirements ensures proper device security from initial deployment and prevents configuration errors during device setup.
Another important aspect of the commit command is how it integrates into Junos OS’s overall configuration management philosophy. Unlike some network operating systems where changes take effect immediately or are written directly into a running configuration, Junos’s commit-based workflow provides a far safer and more controlled environment. This deliberate process ensures that administrators can make changes confidently, knowing they have the opportunity to review, compare, and validate their edits before any impact is felt on live network traffic.
The commit process also supports detailed logging and auditing. Each commit can include a user-supplied comment, which becomes part of the configuration history. These commit logs help organizations track who made changes, when they were made, and why. This is particularly useful for compliance-driven environments and teams that follow strict change-management procedures. In addition, Junos stores multiple previous configurations, allowing administrators to easily revert to earlier states using the rollback command if unexpected behavior occurs after a commit.
Junos also supports advanced commit options for complex environments. For example, commit synchronize ensures that configuration changes on dual Routing Engines (REs) in high-availability systems are applied simultaneously, maintaining state consistency. Similarly, commit at allows scheduling a commit for a future time, which is helpful for planned maintenance windows. These capabilities demonstrate how Junos treats configuration management not as a simple command, but as a comprehensive, flexible system designed to support operational reliability, safety, and efficiency across a wide variety of deployment scenarios.
Question 19
Which Junos configuration mode allows you to make configuration changes?
A) Operational mode
B) Configuration mode
C) Shell mode
D) Monitor mode
Answer: B
Explanation:
Configuration mode is the Junos mode specifically designed for making configuration changes to the device. Administrators enter configuration mode from operational mode by typing the configure command or its shorthand version edit. Once in configuration mode, the prompt changes to include a hash symbol, indicating that configuration commands are now accepted.
In configuration mode, administrators can add, modify, or delete configuration statements using commands like set, delete, edit, and show. The hierarchical nature of Junos configuration allows administrators to navigate through configuration levels using edit commands to move into specific hierarchy levels, up to move up levels, and top to return to the top configuration level.
Configuration mode maintains a candidate configuration that is separate from the active running configuration. This separation allows administrators to make multiple changes, review them using show commands or show compare, and validate them before committing. If mistakes are made, administrators can use rollback 0 to discard all candidate changes or exit configuration mode without committing.
Option A is incorrect because operational mode is used for monitoring, troubleshooting, and viewing information but not for making configuration changes. Option C is wrong as shell mode provides access to the underlying FreeBSD operating system for advanced administration but is not the standard configuration interface. Option D is incorrect because monitor mode is used for traffic monitoring and does not allow configuration changes.
Understanding when and how to use configuration mode is fundamental to Junos device administration and configuration management.
In addition to requiring a root password before the first commit, Junos OS offers several secure methods for configuring root authentication depending on organizational policies. For example, instead of using a plain-text password, administrators can configure an encrypted password by using the set system root-authentication encrypted-password command followed by a pre-hashed password value. This approach avoids entering passwords interactively and is commonly used in automated provisioning workflows, such as Zero Touch Provisioning (ZTP) or scripted deployments. Encrypted password strings can be generated using tools like OpenSSL or through Junos itself using the op scripts or CLI operational commands designed to produce hashed output.
Another increasingly popular option is setting SSH public keys for root authentication using the set system root-authentication ssh-rsa (or other key type) syntax. Key-based authentication reduces reliance on passwords and provides stronger security, particularly for devices accessible over untrusted networks. Many organizations combine SSH keys with centralized authentication mechanisms—such as RADIUS or TACACS+—for administrative users, while maintaining a secure local root credential only for emergency recovery.
It is also important to recognize that Junos prevents the root account from being used for standard remote logins via Telnet or SSH unless explicitly enabled under system services. This reduces the attack surface for brute-force attempts and encourages administrators to create named user accounts with appropriate permissions.
During initial deployment, if an administrator attempts to commit any configuration changes before defining a root password or equivalent authentication method, Junos blocks the commit and clearly indicates the missing requirement. This safeguard ensures that no device enters production without secure administrative access in place. By understanding and following these root authentication requirements, network engineers can adhere to security best practices, avoid setup errors, and ensure that new Junos devices are properly protected from first boot onward.
Question 20
What command is used to view the difference between the candidate configuration and the active configuration?
A) show changes
B) show difference
C) show compare
D) diff configuration
Answer: C
Explanation:
The show compare command displays the differences between the candidate configuration and the currently active running configuration in Junos OS. This command is executed from configuration mode and shows what changes will be activated if the candidate configuration is committed, using a format similar to Unix diff output with plus signs indicating additions and minus signs indicating deletions.
The show compare output helps administrators review all changes before committing them, providing a safety check to ensure that only intended modifications are activated. This is particularly important in production environments where configuration errors could cause service disruptions. Administrators can verify that deletions are intentional and that new configurations are correct before proceeding with the commit.
The show compare command can also be used with a rollback number to compare the candidate configuration against previous configurations, such as show compare rollback 1 to compare against the last committed configuration. This flexibility allows administrators to understand how configurations have evolved over time and verify that current changes align with intended modifications.
Option A is incorrect because show changes is not the correct Junos syntax for comparing configurations. Option B is wrong as show difference is not a valid Junos command for this purpose. Option D is incorrect because diff configuration is not proper Junos command syntax; the correct command is show compare.
Understanding how to review configuration differences before committing is a critical skill for preventing configuration errors and maintaining network stability.
Beyond its standard use, the show compare command in Junos OS offers several advanced features that enhance configuration verification and troubleshooting. Administrators can compare not only the candidate configuration with the active configuration, but also any configuration housed within the rollback archive. For example, show compare rollback 2 allows an engineer to examine how the current candidate differs from a configuration committed two versions earlier. This is especially valuable during audits or when attempting to track down when a particular issue was introduced.
The output of show compare can also be modified using display options. For instance, show compare | display set converts the difference output into set-style commands, which is useful when preparing documentation or when migrating changes to another device that uses script-based deployment. Additionally, when combined with pipe modifiers such as match or except, administrators can narrow down the comparison to specific areas of interest—for example, focusing only on differences related to interfaces or security policies.
Another important capability is comparing configuration groups or template-based configurations. In environments where groups and apply-groups are heavily used, show compare helps reveal both explicit and inherited changes, reducing the likelihood of unintentionally altering shared parameters. This visibility is crucial when multiple administrators collaborate on complex configurations, as it ensures accountability and clarity.
Using show compare before every commit is considered a best practice in Junos environments because it reinforces intentional configuration management. By validating each change in context, engineers significantly reduce the risk of accidental misconfigurations that could lead to outages or degraded network performance.
Question 21
Which file system directory contains Junos OS software packages?
A) /config
B) /var/tmp
C) /var/log
D) /packages
Answer: D
Explanation:
The /packages directory in the Junos file system contains the Junos OS software packages that make up the operating system installation. This directory stores the modular software components that comprise Junos, including the kernel, routing protocols, management daemons, and other system packages. Understanding the package structure is important for software upgrades and troubleshooting.
Junos uses a modular architecture where different functional components are packaged separately, allowing for efficient upgrades and maintenance. The packages directory contains files with extensions like .tgz that represent these modular components. When performing software upgrades, administrators typically place new software images in /var/tmp before using the request system software add command to install them.
Administrators can view installed packages using commands like show version detail or file list /packages/ to see the specific packages that make up the current Junos installation. This information is useful when troubleshooting issues, verifying installations, or understanding which features are available on the device.
Option A is incorrect because /config is not a standard Junos directory; configuration files are typically stored in /config if using separate configuration partitions, but software packages are in /packages. Option B is wrong as /var/tmp is used for temporary files and is often where software images are staged before installation, but not where installed packages reside. Option C is incorrect because /var/log contains log files for system events and troubleshooting, not software packages.
Understanding Junos file system structure helps administrators perform maintenance tasks and troubleshoot system-level issues effectively.
Question 22
What is the purpose of the rollback command in Junos OS?
A) To restart the device
B) To revert to a previous configuration
C) To display system logs
D) To clear the candidate configuration
Answer: B
Explanation:
The rollback command in Junos OS allows administrators to revert to a previous configuration from the configuration rollback history. Junos automatically maintains a history of the last 50 committed configurations numbered from 0 to 49, where rollback 0 is the current active configuration, rollback 1 is the previous configuration, and so on. This feature provides a powerful safety mechanism for recovering from configuration errors.
Administrators use the rollback command in configuration mode followed by a number to load a previous configuration into the candidate configuration. For example, rollback 1 loads the last committed configuration, allowing administrators to review it with show compare before committing to activate it. This process provides an efficient way to undo recent changes or return to a known good configuration state.
The rollback feature is particularly valuable when troubleshooting configuration issues or recovering from mistakes. If a configuration change causes problems, administrators can quickly rollback to the previous working configuration, commit the change, and restore normal operation. The ability to rollback to any of the 50 stored configurations provides flexibility in configuration management.
Option A is incorrect because rollback does not restart the device; it loads a previous configuration into the candidate configuration for review and potential commit. Option C is wrong as displaying logs is done with show log commands, not rollback. Option D is incorrect because while rollback 0 effectively clears changes by reloading the current active configuration, the primary purpose is reverting to previous configurations.
Understanding rollback capabilities is essential for safe configuration management and quick recovery from configuration issues.
Question 23
Which Junos operational mode command displays interface status and statistics?
A) show interfaces
B) display interfaces
C) get interfaces
D) list interfaces
Answer: A
Explanation:
The show interfaces command displays comprehensive interface status and statistics in Junos OS operational mode. This command provides detailed information about physical and logical interfaces including administrative and operational status, protocol state, MAC addresses, IP addresses, traffic statistics, and error counters. It is one of the most frequently used commands for monitoring and troubleshooting network connectivity.
Administrators can use various options with show interfaces to filter or focus output. The command show interfaces terse provides a summary view showing key status information for all interfaces in a compact format. Specific interfaces can be examined with commands like show interfaces ge-0/0/0 to display detailed information for a single interface. Additional modifiers like extensive provide even more detailed statistics.
Interface statistics displayed include input and output packets, bytes, errors, drops, and carrier transitions. This information helps administrators identify performance issues, troubleshoot connectivity problems, verify configuration, and monitor interface utilization. The command can also display specific protocol information for interfaces configured with protocols like MPLS or IPv6.
Option B is incorrect because display interfaces is not valid Junos syntax; display is used as a pipe modifier rather than a base command. Option C is wrong as get interfaces is not proper Junos command syntax for viewing interface information. Option D is incorrect because list interfaces is not a valid Junos operational command.
Understanding how to view and interpret interface information is fundamental for network troubleshooting and monitoring in Junos environments.
Question 24
What is the purpose of the rescue configuration feature in Junos OS?
A) To automatically backup configurations
B) To provide a known good configuration that can be quickly restored
C) To compress configuration files
D) To encrypt sensitive configuration data
Answer: B
Explanation:
The rescue configuration feature in Junos OS allows administrators to save a known good configuration that can be quickly restored in emergency situations. This feature provides a safety mechanism beyond the regular rollback history, offering a dedicated recovery configuration that persists even if the rollback history is cleared or the device is rebooted.
Administrators create a rescue configuration using the request system configuration rescue save command from operational mode. This command captures the current active configuration and stores it as the rescue configuration. When problems occur and standard troubleshooting or rollback options are insufficient, administrators can restore the rescue configuration using request system configuration rescue delete to load it.
The rescue configuration is particularly valuable during major configuration changes, software upgrades, or when making modifications that might prevent normal device access. By saving a rescue configuration before risky changes, administrators ensure they have a reliable recovery path. The rescue configuration persists across reboots and is separate from the normal configuration rollback mechanism.
Option A is incorrect because the rescue configuration is manually created rather than automatic, though automatic backups can be configured separately. Option C is wrong as the rescue configuration is about recovery capability, not compression; Junos stores configurations efficiently regardless of the rescue feature. Option D is incorrect because encryption of sensitive data is handled through separate configuration options, not the rescue configuration feature.
Understanding rescue configuration provides administrators with an additional safety mechanism for managing critical network devices.
Question 25
Which statement is true about Junos OS factory-default configuration?
A) All interfaces are enabled by default
B) A factory-default configuration must be loaded manually
C) The factory-default configuration includes basic system settings and typically has interfaces disabled
D) There is no factory-default configuration
Answer: C
Explanation:
The Junos OS factory-default configuration includes basic system settings necessary for initial device operation, with interfaces typically in a disabled state for security purposes. This default configuration provides a safe starting point that allows administrators to access the device and begin configuration without unintended network connectivity or security exposure.
The factory-default configuration generally includes settings such as the root user account (without password), basic system parameters, and management interface configuration that allows console access. Physical interfaces are administratively disabled by default, requiring explicit configuration and enabling by administrators before they pass traffic. This approach prevents accidental network connections during initial setup.
Administrators can load the factory-default configuration using the command load factory-default in configuration mode if they need to restore a device to its initial state. This is useful when repurposing devices or recovering from severe configuration issues. After loading factory-default, administrators must configure necessary settings including root password, interface configurations, and routing before the device can function in production.
Option A is incorrect because interfaces are disabled by default in the factory configuration, requiring explicit administrator action to enable them. Option B is wrong as the factory-default configuration is present when the device first boots and can be loaded on demand, but is not required to be manually loaded. Option D is incorrect because Junos devices do include a factory-default configuration.
Understanding factory-default configuration helps administrators perform initial device setup and recovery operations safely and effectively.
Question 26
What is the function of the J-Web interface in Junos OS?
A) Command-line interface access
B) Web-based graphical user interface for device management
C) API for automation scripts
D) File transfer protocol service
Answer: B
Explanation:
J-Web is the web-based graphical user interface provided by Junos OS for device management, offering an alternative to the command-line interface for administrators who prefer graphical interaction. J-Web provides access to configuration, monitoring, and troubleshooting functions through a standard web browser, making device management more accessible to administrators with varying experience levels.
Through J-Web, administrators can view device status, monitor interfaces and protocols, configure system settings, manage users, view logs, and perform many other management tasks. The interface presents information in organized panels with graphical representations of statistics and status, making it easier to visualize device operation. J-Web also provides configuration wizards that guide administrators through common setup tasks.
To enable J-Web, administrators must configure it using commands like set system services web-management http or set system services web-management https, with HTTPS being the recommended secure option. J-Web listens on configured ports (default 80 for HTTP, 443 for HTTPS) and requires authentication using device user credentials before granting access to management functions.
Option A is incorrect because command-line interface access is provided through SSH or console connections, not J-Web; J-Web is specifically the graphical web interface. Option C is wrong as API access for automation is provided through NETCONF or REST APIs, not J-Web, though J-Web itself may use APIs internally. Option D is incorrect because file transfer uses FTP, SCP, or SFTP services, not J-Web which is for device management.
Understanding J-Web capabilities provides administrators with flexible management options and can simplify certain management tasks through graphical interaction.
Question 27
Which protocol does Junos OS use for device configuration via API?
A) SNMP
B) NETCONF
C) Telnet
D) HTTP
Answer: B
Explanation:
Junos OS uses NETCONF (Network Configuration Protocol) as the primary API for programmatic device configuration and management. NETCONF is an IETF standard protocol specifically designed for network device configuration that uses XML-based data encoding and operates over secure transport protocols like SSH. Junos has supported NETCONF since its early versions, making it a pioneer in programmable network infrastructure.
NETCONF provides structured access to device configuration and operational data through a standardized interface that automation tools, orchestration systems, and scripts can use reliably. The protocol supports operations like retrieving configuration, modifying configuration, committing changes, and locking configurations to prevent conflicts. Junos exposes its configuration hierarchy through NETCONF using XML schema definitions.
Administrators enable NETCONF by configuring set system services netconf ssh in Junos, which allows NETCONF sessions over SSH on port 830 by default. Automation frameworks like Ansible, Python libraries like ncclient and PyEZ, and orchestration platforms can connect to Junos devices via NETCONF to perform configuration management at scale. This programmability is essential for modern network automation practices.
Option A is incorrect because while SNMP can be used for monitoring and limited configuration, it is not the primary API for configuration management in Junos; NETCONF provides more comprehensive configuration capabilities. Option C is wrong as Telnet is an insecure terminal protocol for interactive CLI access, not an API for programmatic configuration. Option D is incorrect because while HTTP can be used for some management functions, NETCONF is the standard configuration API.
Understanding NETCONF capabilities is increasingly important as network automation and programmability become essential skills for network engineers.
Question 28
What is the purpose of the commit confirmed command in Junos OS?
A) To commit changes permanently
B) To commit changes that automatically rollback unless confirmed within a specified time
C) To verify configuration syntax only
D) To commit without validation
Answer: B
Explanation:
The commit confirmed command in Junos OS provides a safety mechanism that commits configuration changes with an automatic rollback timer, requiring explicit confirmation within a specified time period or the configuration automatically reverts to the previous state. This feature is invaluable when making changes that might inadvertently break connectivity to the device, such as firewall rules or routing changes.
When executing commit confirmed, administrators specify a timeout period (default is 10 minutes) during which they must verify that the changes work as intended and execute a commit command to confirm. If connectivity is lost or the changes cause problems, the automatic rollback ensures the device returns to the working configuration, preventing situations where administrators are locked out of misconfigured devices.
The typical workflow involves executing commit confirmed before risky changes, verifying that connectivity and functionality remain intact, and then executing commit within the timeout period to make the changes permanent. If any issues arise, administrators can simply wait for the timeout or execute rollback to immediately revert. This approach significantly reduces the risk of configuration changes.
Option A is incorrect because commit confirmed is specifically for temporary commits with automatic rollback, not permanent commits without safety mechanisms. Option C is wrong as commit confirmed actually applies the configuration, not just verifies syntax; commit check is used for syntax validation only. Option D is incorrect because commit confirmed performs full validation like any commit operation.
Understanding commit confirmed is essential for making risky configuration changes safely, especially in production environments where connectivity loss could be problematic.
Question 29
Which Junos command displays the current software version running on the device?
A) show version
B) show system
C) display version
D) get version
Answer: A
Explanation:
The show version command displays comprehensive information about the current Junos OS software version running on the device, including the specific release number, build date, hostname, device model, and installed software packages. This command is essential for verifying software versions, planning upgrades, and troubleshooting compatibility issues.
The output of show version includes the Junos version in format like “Junos: 20.4R3.8” indicating the year (20), quarter (4), release type (R for standard release), major version (3), and maintenance version (8). The command also displays the kernel version, platform architecture, copyright information, and the list of installed packages that comprise the Junos installation.
Administrators frequently use show version when opening support cases, as the specific software version is critical information for troubleshooting. The command can also be used with options like show version detail to display additional information about installed packages, or show version invoke-on other-routing-engine to view version information from other routing engines in chassis with redundant control planes.
Option B is incorrect because show system is not the specific command for version information; there are various show system commands for different purposes, but version information requires show version. Option C is wrong as display version is not valid Junos syntax; display is used as a pipe modifier. Option D is incorrect because get version is not proper Junos operational command syntax.
Understanding how to check software versions is fundamental for device maintenance, upgrade planning, and ensuring devices run appropriate software for their role.
Question 30
What is the difference between active and passive monitoring in Junos OS?
A) Active monitoring generates test traffic; passive monitoring observes existing traffic
B) Active monitoring is faster than passive monitoring
C) Passive monitoring requires special hardware
D) There is no difference
Answer: A
Explanation:
Active monitoring in Junos OS involves generating test traffic to measure network performance, connectivity, and service availability, while passive monitoring observes and analyzes existing traffic without injecting additional packets. These complementary approaches serve different purposes in network monitoring and troubleshooting strategies.
Active monitoring techniques include tools like ping and traceroute that send probe packets to test reachability and measure latency, Real-Time Performance Monitoring (RPM) that generates synthetic traffic to measure service-level metrics, and BFD (Bidirectional Forwarding Detection) that sends rapid heartbeat packets to detect failures quickly. These active methods provide controlled testing of network paths and services independent of actual traffic patterns.
Passive monitoring involves capturing and analyzing actual traffic flowing through the device using features like interface statistics, flow monitoring with J-Flow or sFlow, packet capture capabilities, and protocol-specific monitoring. Passive monitoring provides insight into real user traffic patterns, application behavior, and actual network utilization without introducing overhead from test traffic.
Option B is incorrect because speed differences depend on the specific monitoring method and what is being measured, not whether monitoring is active or passive; both approaches have their appropriate use cases. Option C is wrong as passive monitoring does not require special hardware beyond standard device capabilities, though some advanced monitoring features may benefit from additional resources. Option D is incorrect because active and passive monitoring are distinctly different approaches.
Understanding the distinction between active and passive monitoring helps administrators choose appropriate tools and techniques for different troubleshooting and monitoring scenarios.