JN0-106 Operational Monitoring and Maintenance Practice Test 2 — 15 Questions

Question 1

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 2

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 selected because it has a lower metric. In Junos, when multiple routes to the same destination have the same preference (administrative distance), the route with the lower metric is preferred. The exhibit shows two OSPF routes with equal preference, so the metric determines the active route.

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 3

During a network outage, a router is unresponsive via SSH. You have console access but the console displays 'Amnesiac (ttyd0)' prompt. What is the most likely cause and recovery action?

Accepted Answer

The router lost its configuration; load the rescue configuration using 'rollback rescue-config' or 'load override /config/rescue.conf.gz' then commit. The 'Amnesiac (ttyd0)' prompt indicates the router has booted without a valid configuration file in the /config directory. This typically occurs after a 'request system zeroize' command, a failed commit that corrupted the configuration, or a storage issue that prevented the configuration from loading. The recovery action is to load a previously saved rescue configuration using 'rollback rescue' or 'load override /config/rescue.conf.gz' and then commit, which restores the router to a known working state.

Answer

The router's boot device failed; need to replace hardware

Answer

The router booted from backup media; run 'request system software add' to reinstall Junos

Answer

The router's flash memory is corrupted; perform a full reinstall via USB

Question 4

Which TWO commands can be used to monitor system log messages in real-time?

Accepted Answer

monitor start messages. The 'monitor start messages' command streams the contents of the /var/log/messages file in real-time, allowing you to monitor system log messages as they are generated. 'monitor start interactive-commands' (Option D) monitors logs specific to interactive CLI commands, not general system log messages, so it does not satisfy the stem. The other options ('show log messages | last 100', 'show system log messages', 'show configuration system syslog') either display historical data or configuration, not real-time system log monitoring.

Answer

show log messages | last 100

Answer

show system log messages

Answer

show configuration system syslog

Answer

monitor start interactive-commands

Question 5

Which THREE statements are true about the commit operation on Junos?

Accepted Answer

The commit operation validates the configuration before applying.. Option A is correct because the Junos commit operation runs a validation of the candidate configuration against the syntax and constraints of the device's configuration schema before it is applied, rejecting invalid configurations. Option C is correct because, once the commit succeeds, the candidate configuration is activated and becomes the active (running) configuration immediately, without requiring a reboot. Option E is correct because the 'commit check' command performs the same validation as commit without actually activating the candidate configuration, allowing an administrator to verify correctness beforehand. Option B is not among the marked correct answers, and option D is false because commit applies configuration changes live and does not require a reboot.

Answer

The commit operation can be confirmed with a time delay.

Answer

The commit operation always requires a reboot.

Question 6

Refer to the exhibit. Based on the log messages, what is the most likely cause of the interface flapping?

Accepted Answer

Faulty SFP module. The log messages show repeated link up/down events (interface flapping). In Junos, interface flapping is most commonly caused by a faulty SFP module, as physical layer issues like degraded optics or loose connections trigger continuous link transitions. The logs typically show 'link up' followed by 'link down' without any protocol-level errors, pointing to a hardware fault rather than configuration mismatches.

Answer

MTU mismatch

Answer

Duplicate IP address

Answer

Spanning tree topology change

Question 7

Which command displays the version of Junos OS currently running on the device?

Accepted Answer

show version. The 'show version' command is the standard Junos CLI command that displays the Junos OS version currently running on the device, including the software release, build date, and the type of software (e.g., Junos 22.4R2.11). It is the direct equivalent of 'show version' in Cisco IOS and is the primary command for verifying the active software image.

Answer

show system hardware

Answer

show system uptime

Answer

show system information

Question 8

A network engineer notices that the device is not accepting any configuration changes. The engineer suspects the configuration database is locked. Which command can be used to confirm if the configuration is locked and by which session?

Accepted Answer

show system configuration lock. The 'show system configuration lock' command displays information about any current configuration database locks, including the session ID, user, and time the lock was acquired. This directly confirms whether the configuration is locked and by which session, allowing the engineer to identify the blocking session.

Answer

show system rollback compare

Answer

show system commit

Answer

show system database

Question 9

An administrator needs to verify the current time and time zone configured on the Juniper device. Which command should they use?

Accepted Answer

show system clock. The correct command is 'show system clock' because it displays the current system time and time zone configured on the Juniper device. This command is specifically designed to show the local time, time zone offset, and whether daylight saving time is active, making it the precise tool for verifying time and time zone settings.

Answer

show system uptime

Answer

show system information

Answer

show system date

Question 10

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. 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 11

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 12

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. Options C and D are correct because both use the pipe to the save command, which writes the command output to a file for later analysis: 'show interfaces statistics | save /var/log/iface_stats.txt' captures per-interface packet and error counters, and 'show interfaces extensive | save /var/log/iface_extensive.txt' captures the more detailed extensive output including statistics, errors, and configuration data. The 'save' pipe is the Junos mechanism that redirects CLI command output to a named file, so both commands persist current interface statistics to disk. Option A is incorrect because 'file archive interface-statistics' is not a valid command for capturing live interface statistics. Option B is incorrect because 'request system statistics interface' is not a valid operational command that outputs interface statistics. Option E is incorrect because 'monitor interface traffic' displays real-time traffic continuously and does not support the 'save' pipe to write output to a file.

Answer

file archive interface-statistics

Answer

request system statistics interface

Answer

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

Question 13

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

Accepted Answer

show log messages. Option B, 'show log messages', is correct because it is the standard Junos operational command that displays the contents of the messages log file, which contains general system log messages. Option C, 'monitor start messages', is correct because it starts real-time monitoring of the messages log, streaming new system log entries to the terminal as they are generated. Option D, 'show log dm', is correct because 'dm' is the default log file name for the diagnostic/management daemon (mgd) messages, and 'show log dm' displays those system log messages. Option A, 'show system syslog', is not a valid Junos command for viewing log messages (syslog configuration is viewed under 'show configuration system syslog'), and Option E, 'tail -f /var/log/messages', is a Linux/Unix shell command that does not apply to the Junos CLI context of these operational commands.

Answer

show system syslog

Answer

tail -f /var/log/messages

Question 14

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 15

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