JN0-106 Operational Monitoring and Maintenance Practice Test 4 — 15 Questions

Question 1

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. 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 2

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

Accepted Answer

show route. 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 3

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. 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 4

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

Accepted Answer

show log messages. 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 5

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 6

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 7

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 8

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

Accepted Answer

monitor interface traffic. The 'monitor interface traffic' command provides real-time, continuously updating statistics for interface traffic, including packet counts and error rates, which is essential for diagnosing high latency as it allows the administrator to observe changes in real time. Unlike static commands, this dynamic output refreshes automatically, making it ideal for troubleshooting transient issues.

Answer

show interfaces extensive

Answer

show interfaces terse

Answer

show log messages

Question 9

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 10

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. 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 11

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 12

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

Question 13

An administrator suspects that an interface is flapping but the router is remote and the connection is intermittent. The administrator wants to monitor the interface status without maintaining an SSH session. Which approach should be used?

Accepted Answer

Configure event-options to trigger on interface down and send syslog. Junos event-options allows you to define an event policy that triggers on a specific event, such as an interface down transition, and then executes an action like sending a syslog message. This enables asynchronous monitoring without requiring an active SSH session, making it ideal for intermittent connectivity scenarios.

Answer

Use 'monitor interface ge-0/0/0' and rely on terminal persistence

Answer

Use 'monitor start' to capture logs

Answer

Schedule a cron job to run 'show interfaces ge-0/0/0' every minute and log output

Question 14

A Juniper device is running out of disk space on the /var partition. Which command can be used to check disk usage?

Accepted Answer

show system storage. The correct command to check disk usage on a Juniper device is 'show system storage'. This command displays detailed information about disk partitions, including total, used, and available space, as well as the percentage of usage for each mounted filesystem, such as /var. It is the standard operational mode command for monitoring storage utilization in Junos OS.

Answer

show system disk-space

Answer

show system memory

Answer

show system resource

Question 15

Which THREE operational commands are used to monitor interface statistics and status? (Select three.)

Accepted Answer

show interfaces terse. 'show interfaces terse' provides a concise summary of all interfaces, including their administrative and operational status (up/down) and protocol states, making it ideal for a quick health check. Option B is correct because 'monitor interface' is a real-time operational command that continuously displays interface statistics and status updates, useful for live traffic observation. Option C is correct because 'show interfaces' displays detailed interface statistics, including packet counts, errors, and operational status, which is the primary command for in-depth interface monitoring.

Answer

show log interfaces

Answer

show interfaces diagnostics