JN0-106 Operational Monitoring and Maintenance Practice Test 6 — 15 Questions

Question 1

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

Accepted Answer

show route. Option C, `show route`, is correct because on Junos devices this command displays the complete routing table, which by default is the IPv4 unicast table (inet.0), listing all learned and direct routes. Option D, `show route table inet.0`, is also correct because inet.0 is the specific routing table name for IPv4 unicast routes, so this command explicitly displays exactly that table. Option A, `show ip route`, is not a valid Junos command (it is Cisco IOS syntax), so it does not belong. Option B, `show route protocol ospf`, only filters and displays OSPF-learned routes rather than the entire IPv4 unicast routing table. Option E, `show routing`, is not a valid command and therefore cannot display the routing table.

Answer

show ip route

Answer

show route protocol ospf

Answer

show routing

Question 2

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 3

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 4

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 5

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 6

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 7

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 messages. 'show log messages' is the standard JUNOS command to display the contents of the /var/log/messages file. While it does not include a filter, it is the only valid command among the options that allows the administrator to view existing system log messages. The other options are either invalid commands (B and D) or used for real-time monitoring (A), which is not efficient for checking historical log files.

Answer

monitor start messages | match "error"

Answer

show log file messages | match "error"

Answer

show system syslog messages

Question 8

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 9

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 10

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

Accepted Answer

show interfaces terse. Option A, "show interfaces terse," is correct because it provides a compact, one-line-per-interface summary of operational status (up/down), protocol state, and basic counters, making it ideal for quickly monitoring interface status. Option B, "monitor interface," is correct because it displays real-time, continuously updating interface statistics and status, which is specifically designed for live monitoring of interface traffic and errors. Option C, "show interfaces," is correct because it gives detailed operational output including status, protocol state, error counters, and statistics for each interface, serving as a primary monitoring command. Option D, "show log interfaces," is not a valid operational command for monitoring interface statistics and status; logs are viewed with commands like "show log messages." Option E, "show interfaces diagnostics," is not a standard command for monitoring interface statistics and status; diagnostics commands typically display optics or hardware diagnostic information rather than general interface status and counters.

Answer

show log interfaces

Answer

show interfaces diagnostics

Question 11

Which TWO methods can be used to restore a previous configuration on a Juniper device? (Select two.)

Accepted Answer

load override /config/rescue.conf. Option A, `load override /config/rescue.conf`, is correct because the rescue configuration is a saved, known-good configuration file that can be loaded with the `load override` command to replace the entire current candidate configuration, after which a `commit` restores the device to that prior state. Option C, `rollback 1`, is correct because Junos retains the last 49 committed configurations, and `rollback 1` loads the immediately previous committed configuration into the candidate, which can then be committed to restore the earlier configuration. Option B, `commit confirmed`, is not a restore method; it activates a configuration temporarily and auto-rolls back unless confirmed, so it is used for safe changes, not for restoring a previous config. Option D, `load replace previous`, is invalid syntax—`load replace` requires a specific file or terminal input, and there is no `previous` keyword for it. Option E, `rollback 0`, loads the currently active (most recent) committed configuration, so it does not restore an earlier configuration.

Answer

commit confirmed

Answer

load replace previous

Answer

rollback 0

Question 12

Your company runs a Juniper MX480 router as the core gateway. The router has been experiencing intermittent connectivity issues with a remote site over a point-to-point OC3 link. Users report that the link goes down for a few seconds several times a day. You suspect that the issue might be related to physical layer errors or framing. You need to determine the cause and collect relevant data to present to the service provider. Which course of action should you take first?

Accepted Answer

Run 'monitor interface so-0/0/0' and observe for any CRC errors or alarms over a period of time.. 'monitor interface so-0/0/0' provides real-time, continuous display of interface counters and alarms, allowing you to observe CRC errors, framing errors, or alarms (e.g., LOS, LOF) as they occur. This is the most direct way to capture transient physical-layer issues on a SONET/SDH OC3 link without disrupting service, making it the appropriate first step before escalating to the service provider.

Answer

Perform a loopback test on the interface using 'test interface so-0/0/0'.

Answer

Review the system syslog file using 'show log messages' and search for interface down messages.

Answer

Immediately replace the serial interface card to rule out hardware failure.

Question 13

You are a junior network engineer tasked with upgrading the Junos OS on a pair of EX3400 switches that are in a Virtual Chassis. You have downloaded the new software image to the primary switch. Before performing the upgrade, you must verify the image's integrity and check the current version. Which sequence of commands should you use?

Accepted Answer

Run 'show version' and then 'request system software validate /var/tmp/junos-new.tgz'.. 'show version' displays the current Junos OS version running on the switch, which is necessary to confirm the starting point before an upgrade. Then 'request system software validate /var/tmp/junos-new.tgz' performs a checksum verification and package integrity check on the image file without installing it, ensuring the image is not corrupted. This sequence directly addresses the two tasks: verifying the image's integrity and checking the current version.

Answer

Run 'show system uptime' and then 'request system software add /var/tmp/junos-new.tgz'.

Answer

Run 'show system software' and then 'request system software add validate'.

Answer

Run 'show configuration system software' and then 'file checksum sha256 /var/tmp/junos-new.tgz'.

Question 14

Which two commands can be used to monitor real-time interface statistics and errors on a Junos device?

Accepted Answer

show interfaces extensive ge-0/0/0 | refresh 1. Option C, 'show interfaces extensive ge-0/0/0 | refresh 1', is correct because the 'extensive' keyword displays detailed statistics including error counters, and the '| refresh 1' pipe re-runs the command every second, giving real-time monitoring of a specific interface. Option D, 'monitor interface ge-0/0/0', is correct because the 'monitor interface' command is Junos's dedicated real-time interface statistics viewer, continuously updating counters such as packets, bytes, and errors for the named interface. Option A, 'show interfaces terse', only gives a one-time summary of interface status and addresses without error detail or refresh, so it is not real-time monitoring. Option B, 'show interfaces ge-0/0/0', provides a single snapshot of standard statistics and does not refresh or emphasize error counters. Option E, 'monitor security log', streams security log messages rather than interface statistics and errors, so it does not meet the requirement.

Answer

show interfaces terse

Answer

show interfaces ge-0/0/0

Answer

monitor security log

Question 15

A network administrator notices that the CPU utilization on an MX240 router has been consistently above 90% for the past hour. Users are reporting intermittent connectivity issues. The administrator logs in and runs 'show system processes extensive' which shows the Routing Protocol Daemon (rpd) consuming 70% of the CPU. Further investigation reveals that the router has over 5000 BGP prefixes from multiple peers. The administrator suspects that the high CPU is due to continuous route processing. What should the administrator do to immediately reduce CPU load while maintaining network stability?

Accepted Answer

Apply a prefix-limit on each BGP session to restrict the number of prefixes received. Applying a prefix-limit on each BGP session immediately restricts the number of prefixes the router will accept from peers. This prevents the Routing Protocol Daemon (rpd) from processing excessive BGP updates, reducing CPU load while maintaining network stability by keeping existing sessions and routes intact. The prefix-limit action (e.g., with a teardown threshold) ensures the router does not accept more prefixes than it can handle, directly addressing the root cause of high CPU usage.

Answer

Perform a 'show log messages' to check for errors before taking action

Answer

Bounce all BGP sessions by clearing them with 'clear bgp neighbor *'

Answer

Disable BGP multipath to reduce route processing