JNCIA-JUNOS Operational Monitoring and Maintenance Practice Test 5 — 15 Questions

Question 1

A network administrator is troubleshooting a routing issue and wants to view the routing table for a specific routing instance called 'VPN-A'. Which command should they use?

Accepted Answer

show route table VPN-A. The correct command to view the routing table for a specific routing instance in Junos is 'show route table VPN-A'. This command displays the routes associated with the routing instance named 'VPN-A', which is essential for troubleshooting routing issues within that instance. The 'show route' command is the standard way to view routing tables, and specifying the 'table' keyword followed by the instance name targets the correct routing table.

Answer

show routing-table VPN-A

Answer

show route instance VPN-A

Answer

show routing instance VPN-A route

Question 2

An engineer needs to check if the device has any pending changes that have not been committed. Which operational command should they run?

Accepted Answer

show configuration | compare. Option C is correct because the 'show configuration | compare' command displays the differences between the candidate configuration (changes made but not yet committed) and the active configuration. This allows the engineer to see any pending changes that have not been committed, which is exactly what the question asks.

Answer

show system configuration

Answer

show system rollback

Answer

show system commit

Question 3

A network technician needs to clear all BGP sessions and force BGP to re-establish peering relationships. Which command should they use?

Accepted Answer

clear bgp all. Option C is correct because the 'clear bgp all' command in Junos resets all BGP sessions by clearing the BGP routing table and forcing the protocol to re-establish peering relationships from scratch. This is the standard Junos command to tear down and restart all BGP adjacencies, triggering new OPEN messages and route exchanges.

Answer

clear bgp summary

Answer

clear bgp restart

Answer

clear bgp statistics

Question 4

Which two commands display the IPv4 unicast routing table? (Choose two.)

Accepted Answer

show route. Option C is correct because the 'show route' command without any filters displays the entire IPv4 unicast routing table (inet.0) by default in Junos OS. Option D is correct because 'show route table inet.0' explicitly targets the main IPv4 unicast routing table, which is the default routing instance's inet.0 table.

Answer

show ip route

Answer

show route protocol ospf

Answer

show routing

Question 5

Which two commands can be used to capture the current interface statistics and save them for later analysis? (Choose two.)

Accepted Answer

show interfaces statistics | save /var/log/iface_stats.txt. Option C is correct because the 'show interfaces statistics' command displays current interface counters (e.g., input/output packets, errors, discards) and piping the output to '| save /var/log/iface_stats.txt' writes the snapshot to a file for later analysis. This allows you to capture a point-in-time record of interface statistics without ongoing monitoring.

Answer

file archive interface-statistics

Answer

request system statistics interface

Answer

monitor interface traffic | save /var/log/iface_traffic.txt

Question 6

Which three commands can be used to view system log messages? (Choose three.)

Accepted Answer

show log messages. Option B is correct because the 'show log messages' command displays the contents of the /var/log/messages file, which is the primary system log file on Junos OS. This file contains kernel messages, system startup events, and other critical operational logs, making it a standard way to view system log messages.

Answer

show system syslog

Answer

tail -f /var/log/messages

Question 7

Refer to the exhibit. Which interface(s) have a physical layer issue?

Accepted Answer

ge-0/0/1 only. The 'Physical link is Down' status on ge-0/0/1 indicates a Layer 1 issue, such as a disconnected cable, faulty transceiver, or powered-down remote device. The other interfaces show 'Up' physical status, confirming they have no physical layer problem.

Answer

ge-0/0/0 only

Answer

ge-0/0/0 and ge-0/0/2

Answer

ge-0/0/2 only

Question 8

Refer to the exhibit. Based on the log output, what is the most likely issue with interface ge-0/0/1?

Accepted Answer

Interface is experiencing flapping. The log output shows repeated 'link UP' and 'link DOWN' events for interface ge-0/0/1 within a short time window, which is the classic symptom of interface flapping. Flapping typically occurs due to physical layer issues such as faulty cables, damaged transceivers, or marginal signal integrity, causing the interface to continuously transition between up and down states.

Answer

Interface is up and stable

Answer

Interface is administratively down

Answer

Interface is configured incorrectly

Question 9

Refer to the exhibit. An engineer is trying to commit a configuration but receives a 'no space left on device' error. Which filesystem is most likely full?

Accepted Answer

/var. The /var filesystem on Junos stores log files, core dumps, and other operational data. When the device runs out of disk space, it is most commonly the /var partition that is full, as it accumulates logs and crash files over time. The 'no space left on device' error during a commit indicates that the system cannot write the new configuration to the /var/tmp or /var/db/config directory, which reside under /var.

Answer

/config

Answer

/tmp

Answer

/dev

Question 10

A network administrator is troubleshooting high latency on a link. Which command provides real-time interface statistics?

Accepted Answer

monitor interface traffic. Option B is correct because 'monitor interface traffic' shows live traffic statistics. Option A shows a static brief summary. Option C shows detailed but static output. Option D shows historical log messages.

Answer

show interfaces extensive

Answer

show interfaces terse

Answer

show log messages

Question 11

A network engineer needs to analyze NTP synchronization status and offset. Which command provides detailed NTP peer information including delay, offset, and jitter?

Accepted Answer

show ntp associations. The 'show ntp associations' command displays detailed NTP peer information, including delay, offset, and jitter, which are essential for analyzing synchronization status. This command lists all configured NTP peers and their current state, providing the specific metrics needed to assess clock accuracy and stability.

Answer

show ntp statistics

Answer

show ntp status

Answer

show ntp peer

Question 12

After a configuration change, a router is not behaving as expected. The administrator wants to rollback to the previous configuration. Which command accomplishes this?

Accepted Answer

rollback 1. Option C is correct because the 'rollback 1' command reverts the active configuration to the most recent committed configuration (the one before the latest commit). In JUNOS, the rollback command uses a numeric index where 0 is the current active configuration, 1 is the previous committed configuration, and higher numbers go further back. This allows the administrator to undo an unwanted configuration change without manually editing the configuration.

Answer

rollback 0

Answer

commit check

Answer

load override current

Question 13

A technician needs to monitor routing table updates in real time. Which command provides continuous output of routing changes?

Accepted Answer

monitor route. The 'monitor route' command in Junos provides a real-time, continuously updating view of routing table changes as they occur. Unlike static commands that show a snapshot, this command actively tracks route additions, removals, and modifications, making it the correct choice for monitoring routing updates in real time.

Answer

show log messages | match route

Answer

show route

Answer

show route protocol bgp

Question 14

An administrator is asked to check the system log files for any error messages related to interface failures. Which command would be most efficient?

Accepted Answer

show log file messages | match "error". Option B is correct because 'show log messages' displays the contents of the /var/log/messages file, and piping the output to 'match "error"' filters for lines containing 'error', making it the most efficient command to check system log files for interface failure errors. The 'show log' command is the standard way to view log files in JUNOS, and the 'match' filter allows targeted searching without overwhelming the administrator with irrelevant data.

Answer

monitor start messages | match "error"

Answer

show log messages

Answer

show system syslog messages

Question 15

A network engineer is performing a software upgrade on an MX router. Before upgrading, which operational command should be used to verify the current software version and the upgrade file?

Accepted Answer

show version. The 'show version' command displays the currently running Junos OS version, including the software build and release information. Before upgrading, you must verify the current version to ensure compatibility with the upgrade file, and the upgrade file itself is typically referenced by its filename or path, not shown by this command. To check the upgrade file, you would use 'file list' or 'show system software' to list available packages, but for the current version, 'show version' is the correct operational command.

Answer

show configuration system software

Answer

show system upgrade

Answer

show system software