JN0-106 Operational Monitoring and Maintenance Practice Test 3 — 15 Questions

Question 1

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 2

Which TWO commands can be used to view the system log messages on a Juniper device? (Select two.)

Accepted Answer

show log messages. Option B, 'show log messages', is correct because on Junos devices the main system log file is named 'messages', and the 'show log messages' command displays its contents, including general system, daemon, and kernel messages. Option C, 'monitor start messages', is correct because the 'monitor start' command streams real-time log output to the terminal, and specifying 'messages' tails the main system log as new entries are written. Option A, 'show log dcd', is incorrect because 'dcd' is the Device Control Daemon log, which only shows interface/configuration-related messages rather than the full system log. Option D, 'show log file', is incorrect because 'file' is not a valid Junos log filename and the syntax does not reference an actual log. Option E, 'show system messages', is incorrect because 'show system' is used for hardware/process information and does not display log file contents.

Answer

show log dcd

Answer

show log file

Answer

show system messages

Question 3

You are a network administrator for a large enterprise. The Juniper EX4300 switch that serves as the distribution layer for the finance department is experiencing high CPU utilization. Users are complaining of slow network performance. You have accessed the switch via console and notice that the CPU load is consistently above 90%. You need to identify the process causing the high CPU usage. Which command should you use?

Accepted Answer

'show system processes' to list all processes and their CPU usage.. The 'show system processes' command displays a list of all running processes along with their CPU and memory usage, allowing you to identify which process is consuming excessive CPU resources. This is the direct method to pinpoint the offending process on a Juniper EX4300 switch running Junos OS.

Answer

'show task summary' to see kernel task CPU usage.

Answer

'show system resources' to check memory and CPU.

Answer

'show system statistics' to view overall system stats.

Question 4

A Juniper SRX300 firewall is deployed at a branch office. The firewall's disk space on /var is critically low, causing logs to stop writing and system performance degradation. You need to free up space quickly without deleting logs (they are required for compliance). Which action should you take?

Accepted Answer

Compress old log files using 'request system storage compress'.. The 'request system storage compress' command compresses inactive log files on the /var partition, freeing up disk space without deleting any logs. This preserves the logs for compliance requirements while immediately alleviating the low disk space condition. The command targets files that are not currently being written to, such as rotated or archived logs, and compresses them using gzip.

Answer

Increase the /var partition size using LVM.

Answer

Enable log rotation with smaller retention to prevent future growth.

Answer

Move logs to an NFS mount using 'file copy' and delete local copies.

Question 5

A service provider has two MX routers (R1 and R2) connected via two separate physical links. Both links are in an aggregated Ethernet bundle (ae0). The ae0 interface is configured with LACP active on both sides. Recently, a fiber cut occurred on one of the member links, and the aggregated interface continued working. However, after the fiber was repaired, the network operator noticed that the restored link is not being re-added to the bundle. 'show lacp interfaces' indicates the link is in a 'detached' state. The operator checks 'show interfaces diagnostics optics' and finds that the optical parameters are normal. Which action should the operator take to restore the link to the bundle without affecting traffic?

Accepted Answer

Remove and re-add the member link from the ae0 configuration. The 'detached' state indicates LACP negotiation failed or is stuck, even though the physical link is up. The proper fix is to reinitialize LACP on that member link. In Junos, 'clear lacp interfaces' accomplishes this, but that command is not offered as an option. Option B, removing and re-adding the member link from the ae0 configuration, forces the interface to be re-created and LACP to restart. Because the link is already detached and not forwarding traffic, this action does not affect active traffic on the bundle.

Answer

Reboot the router to clear all LACP states

Answer

Issue the 'clear lacp statistics' command on the interface to reset LACP negotiation on that link

Answer

Replace the SFP module on the restored link

Question 6

An engineer needs to check for packet errors on an interface. Which two commands provide error counter information? (Choose two.)

Accepted Answer

show interfaces extensive. Option C, 'show interfaces extensive', is correct because on Junos devices it displays the complete, detailed output for an interface including the error counters (input errors, output errors, CRC/Frame errors, collisions, drops, etc.) that the engineer needs to check for packet errors. Option D, 'show interfaces errors', is correct because it is the Junos command specifically intended to display interface error statistics, summarizing error counters per interface so the engineer can quickly identify packet errors. The unmarked options do not belong: 'show interfaces diagnostics' (A) shows transceiver/optics diagnostic data such as temperature, voltage, and laser bias rather than packet error counters; 'show interface errors' (B) is not a valid Junos command (the correct form is 'show interfaces errors'); and 'show interfaces terse' (E) only gives a brief up/down and address summary without error counter details.

Answer

show interfaces diagnostics

Answer

show interface errors

Answer

show interfaces terse

Question 7

Refer to the exhibit. A network administrator notices intermittent connectivity issues. Based on the log messages, what is the most likely cause?

Accepted Answer

The interface ge-0/0/0 is experiencing a physical layer issue causing it to flap.. The log shows rapid down/up events (flapping) on interface ge-0/0/0. This pattern typically indicates a physical layer problem such as a faulty cable or transceiver. Option B is plausible but the traps are symptoms, not the cause. Option C is less likely because the adjacency recovers quickly. Option D is unsupported by the logs.

Answer

The ISIS protocol has a configuration error that prevents adjacency.

Answer

An SNMP trap is causing a loop in the network.

Answer

The router's MIB is corrupted causing false logs.

Question 8

A company runs Juniper MX routers in a data center. They have a monitoring server that polls SNMP every 5 minutes. Recently, the monitoring server reported that interface ge-0/0/1 on router R1 has been down for 3 hours, but the network operations center says that no alarms were triggered and the link appears up from their end. The administrator logs into R1 and runs 'show interfaces ge-0/0/1' and sees that the interface is up with no errors, but the output shows 'Last flapped: 3 hours ago', which matches the monitoring downtime. Further investigation reveals that the interface has been administratively disabled and re-enabled at that time by an automated script that was later rolled back. The monitoring server uses ifAdminStatus and ifOperStatus OIDs. Which action would most reliably prevent this false positive in the future?

Accepted Answer

Monitor ifLastChange OID along with ifOperStatus to detect administrative flapping.. To prevent false positives from administrative interface down events, the monitoring system should correlate ifAdminStatus with ifOperStatus and suppress alarms when ifAdminStatus is down. ifLastChange only reflects changes to ifOperStatus and cannot indicate whether a down event was caused by an administrative action. The provided explanation incorrectly claims ifLastChange can detect administrative flapping.

Answer

Use 'show interfaces extensive' to confirm interface status.

Answer

Change the SNMP polling interval to 1 minute.

Answer

Disable the automated script that caused the administrative disable.

Question 9

A network engineer notices that a device is not sending SNMP traps to the NMS. Which operational command should be used to verify SNMP configuration?

Accepted Answer

show snmp. The 'show snmp' command in Junos displays the current SNMP configuration, including community strings, trap destinations, and enabled trap groups. Since the issue is that the device is not sending SNMP traps, this command allows the engineer to verify that trap destinations are correctly configured and that the appropriate trap groups are enabled. Other commands like 'show system uptime' or 'show route' do not provide any SNMP-specific configuration details.

Answer

show system uptime

Answer

show route

Answer

show interfaces terse

Question 10

A network administrator is troubleshooting high CPU usage on a Juniper router. Which command helps identify which process is consuming the most CPU?

Accepted Answer

show system processes extensive. The 'show system processes extensive' command displays detailed information about all running processes, including CPU utilization, memory usage, and process IDs. This allows the administrator to identify which process (e.g., routing protocol daemon, management daemon) is consuming the most CPU cycles, directly addressing the troubleshooting need.

Answer

show log messages

Answer

show system memory

Answer

show interfaces

Question 11

A junior engineer needs to collect a snapshot of the current system state, including routing tables, interfaces, and configuration, for a support ticket. Which command achieves this?

Accepted Answer

request support information. The 'request support information' command is the correct choice because it collects a comprehensive snapshot of the current system state, including routing tables, interface details, configuration, logs, and other operational data into a single archive file. This is specifically designed for support tickets, as it bundles all relevant diagnostic information in one step, unlike individual show commands that only capture partial data.

Answer

show configuration

Answer

show interfaces

Answer

show route

Question 12

A network engineer wants to schedule a reboot of a Juniper device at 3:00 AM. Which command should be used?

Accepted Answer

request system reboot at 03:00. The 'request system reboot at 03:00' command schedules a one-time reboot of the Juniper device at the specified time (3:00 AM). The 'at' parameter allows the engineer to set an absolute time for the reboot, which is the exact requirement for scheduling a reboot at a specific future time.

Answer

request system configuration rescue save

Answer

request system reboot

Answer

load override /config/juniper.conf.gz

Question 13

A router is experiencing intermittent packet loss. The engineer runs 'show interfaces ge-0/0/0 extensive' and notices a high number of input errors but no output errors. What is the most likely cause?

Accepted Answer

A faulty transceiver. A high number of input errors with no output errors on a Juniper interface typically indicates a Layer 1 issue at the receiving end. A faulty transceiver can cause signal degradation, leading to CRC errors, framing errors, or alignment errors, all of which are counted as input errors. Since output errors are absent, the problem is not with the router's transmission but with the incoming signal quality.

Answer

The cable is too long

Answer

MTU mismatch

Answer

The interface is oversubscribed

Question 14

An engineer needs to check the last time the configuration was changed. Which command provides this information?

Accepted Answer

show system commit. The 'show system commit' command displays the commit history, including the date, time, and user for each configuration change. This allows the engineer to see exactly when the last configuration was committed, which is the definitive way to determine the last time the configuration was changed.

Answer

show configuration | display set

Answer

show system alarms

Answer

show system uptime

Question 15

A BGP session is flapping. The engineer runs 'show log messages' and sees 'BGP recv Notification' with error code 'Cease'. What does this indicate?

Accepted Answer

The remote peer closed the connection. A BGP Cease notification indicates that the remote peer has closed the BGP session, often due to an administrative shutdown, configuration change, or error condition on the peer. The 'BGP recv Notification' message means the local router received this notification from the peer, so the remote peer initiated the closure.

Answer

The BGP table is full

Answer

The hold timer expired

Answer

The interface went down