JNCIA-JUNOS Operational Monitoring and Maintenance Practice Test 3 — 15 Questions

Question 1

During a maintenance window, an engineer plans to replace a line card. Which command sequence is most appropriate to gracefully deactivate the card before removal?

Accepted Answer

request chassis pic slot offline; request chassis fpc offline. Option A is correct because the 'request chassis fpc offline' command gracefully deactivates the Flexible PIC Concentrator (FPC) by stopping traffic, closing sessions, and powering down the line card safely. The 'request chassis pic slot offline' command is used for individual PICs, but for a full line card (FPC), the FPC-level command is the appropriate sequence to ensure no traffic disruption or hardware damage during removal.

Answer

delete interfaces fxp0

Answer

set interfaces <name> disable

Answer

request system reboot

Question 2

An administrator observes that the router's CPU utilization is consistently high. Which command helps identify which process is consuming the most CPU?

Accepted Answer

show system processes extensive. Option D, 'show system processes extensive', is correct because it displays detailed CPU utilization statistics for each running process on a Junos device, including the percentage of CPU time consumed. This allows the administrator to identify which specific process (e.g., routing protocol daemon, SNMP, or management process) is causing the high CPU load, enabling targeted troubleshooting.

Answer

show log messages

Answer

show system resource

Answer

show chassis routing-engine

Question 3

A network engineer needs to verify the checksum of a downloaded Junos image before installation. Which command is used?

Accepted Answer

file checksum sha256 . Option A is correct because the `file checksum sha256 ` command computes the SHA-256 hash of the specified file, allowing the engineer to compare it against the published checksum from Juniper Networks to verify integrity and authenticity before installation. This ensures the image has not been corrupted or tampered with during download.

Answer

compare <filename> original

Answer

request system software validate <filename>

Answer

show system software

Question 4

Which two commands can be used to display real-time interface information? (Choose two.)

Accepted Answer

monitor interface. The `monitor interface` command provides a real-time, continuously updating view of interface statistics, including traffic counters, errors, and operational status. The `monitor traffic` command captures and displays live packet headers or full packets on an interface, useful for real-time traffic analysis. Both commands are designed for live monitoring, unlike static `show` commands or administrative actions.

Answer

show log

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request system reboot

Answer

show system storage

Question 5

Which two events typically trigger a change to the routing table? (Choose two.)

Accepted Answer

Interface state change. An interface state change (up/down) directly affects the reachability of directly connected networks, causing Junos to add or remove the corresponding routes from the routing table. Similarly, a BGP neighbor reset tears down and re-establishes the TCP session, which triggers the withdrawal and re-advertisement of all BGP routes, thus modifying the routing table.

Answer

System uptime

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Log file rotation

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Configuration commit

Question 6

Which three steps are part of a typical software upgrade process on a Juniper device? (Choose three.)

Accepted Answer

Issue the request system software add command. Option A is correct because the 'request system software add' command is the standard Junos CLI command used to initiate the installation of a new software image on a Juniper device. This command triggers the process of copying the image from a specified source (e.g., a URL or local file) into the system's active software partition, preparing it for the next reboot.

Answer

Shut down all interfaces

Answer

Delete the old image before adding the new one

Question 7

Refer to the exhibit. An engineer notices that input drops are increasing. What is the most likely cause?

Accepted Answer

Buffer overflow. Input drops occur when the ingress interface's receive buffer is full and cannot accept more packets, typically due to the ingress rate exceeding the interface's ability to process or forward packets to the internal switch fabric. In Junos, this is often caused by microbursts or sustained oversubscription, not by a speed mismatch (which would show as errors or link flaps) or cable faults (which cause physical-layer errors). Buffer overflow is the correct answer because input drops directly indicate that the packet buffer has been exhausted.

Answer

Speed mismatch

Answer

Cable fault

Answer

CRC errors

Question 8

Refer to the exhibit. What is the most likely cause of the BGP session failure?

Accepted Answer

Hold timer expired due to delayed keepalives. The BGP session failure is most likely due to the hold timer expiring because keepalive messages were not received in time. In JUNOS, the default hold time is 90 seconds, and if a router does not receive a keepalive or update within that interval, it declares the peer dead and resets the session. The exhibit shows the BGP state as 'Idle' or 'Active', which is consistent with a hold timer expiry event.

Answer

The peer is unreachable

Answer

BGP configuration mismatch

Answer

Route flapping

Question 9

Refer to the exhibit. Which route will be used to forward traffic to 192.168.1.0/24?

Accepted Answer

The route via 10.0.0.2 because it has a lower metric. The route via 10.0.0.2 is correct because Junos uses the route preference (administrative distance) to select the best route when multiple routes to the same destination exist. OSPF has a default preference of 10, while static routes have a default preference of 5, but here the static route via 10.0.0.2 has a metric of 0 (lower than OSPF's metric of 2), and since both are active, the lower metric does not override preference; however, the exhibit shows the static route is preferred because it has a lower preference value (5 vs 10), making it the active route in the routing table.

Answer

Neither route is valid

Answer

The route via 10.0.0.1 because it was learned later

Answer

Both routes are used for load balancing

Question 10

A network administrator wants to see the current CPU load average over the last 1, 5, and 15 minutes on a Juniper device. Which command displays this information?

Accepted Answer

show system uptime. The 'show system uptime' command displays the system's uptime along with the load averages for the last 1, 5, and 15 minutes. This is the standard Junos command for viewing CPU load averages, which are calculated based on the number of processes in the run queue over those time intervals.

Answer

show chassis routing-engine

Answer

show system processes

Answer

show system statistics

Question 11

A technician notices that the /var partition is filling up on a Juniper device. Which action would be most appropriate to free up space while preserving critical logs?

Accepted Answer

Run 'request system storage cleanup'. The 'request system storage cleanup' command is the correct action because it safely removes non-essential files such as old log files, core dumps, and temporary files that are no longer needed, while preserving critical logs and configuration files. This command performs a controlled cleanup without risking the deletion of important operational data, making it the most appropriate method for freeing up space on the /var partition.

Answer

Delete core files manually

Answer

Reboot the device

Answer

Delete all files in /var/log

Question 12

A network operator needs to upgrade the Junos OS on the backup RE (re1) of a dual-RE system. Which procedure ensures that only the backup RE is upgraded and rebooted without affecting the forwarding plane?

Accepted Answer

Use 'request system software add re1' and then 'request system reboot re1'. Option A is correct because the 'request system software add re1' command installs the Junos OS image only on the backup Routing Engine (RE1), and the subsequent 'request system reboot re1' reboots only that RE. In a dual-RE system, this procedure isolates the upgrade to the backup RE, ensuring the forwarding plane remains active on the primary RE (RE0) and no traffic disruption occurs.

Answer

Use 'request system software add <image> both' and then 'request system reboot both'

Answer

Use 'request system software add <image> re0' and then 'request system reboot re0'

Answer

Copy the image to both REs and reboot the backup RE with 'request system reboot slice 1'

Question 13

Which command displays the status of all configured interfaces, including administrative and operational status?

Accepted Answer

show interfaces terse. The 'show interfaces terse' command displays a concise summary of all interfaces, including their administrative status (up or down) and operational status (up or down), along with protocol states. This makes it the correct choice for quickly viewing the status of all configured interfaces in a single output.

Answer

show configuration interfaces

Answer

show chassis hardware

Answer

show interface statistics

Question 14

A network engineer suspects a hardware issue on an interface. Which command provides the most detailed hardware error counters, including CRC errors, framing errors, and runts?

Accepted Answer

show interfaces extensive. The 'show interfaces extensive' command provides the most detailed hardware error counters for a Junos interface, including CRC errors, framing errors, and runts. This command displays per-interface statistics at the physical layer, such as input errors, output errors, and specific error types like frame, runts, giants, and CRC errors, which are essential for diagnosing hardware issues.

Answer

show interfaces diagnostics optics

Answer

show interfaces detail

Answer

show log messages

Question 15

An operator wants to monitor the temperature and voltage sensors on a Juniper chassis. Which command displays current sensor readings?

Accepted Answer

show chassis environment. The 'show chassis environment' command displays real-time sensor readings for temperature, voltage, and fan status on Juniper devices. It is the standard operational command for monitoring chassis environmental health, directly matching the operator's requirement to check temperature and voltage sensors.

Answer

show chassis hardware

Answer

show system health

Answer

show log messages | match temperature