JN0-106 Junos OS Fundamentals — 10 Questions

Question 1

A network engineer is configuring a new Juniper device and needs to ensure that the configuration is saved persistently across reboots. Which command should be used?

Accepted Answer

commit. The `commit` command activates the candidate configuration and saves it to the active configuration database, ensuring it persists across reboots. Without a commit, any changes made in candidate mode are lost when the device restarts.

Answer

save

Answer

request system reboot

Answer

show configuration

Question 2

An administrator needs to quickly revert all uncommitted configuration changes and return the device to the last committed configuration. Which command accomplishes this?

Accepted Answer

rollback 0. The command 'rollback 0' reverts all uncommitted configuration changes and returns the device to the last committed configuration. In Junos, the rollback command uses a numeric argument to specify which previous configuration to load, with 0 always referring to the most recently committed configuration. This effectively discards any pending changes in the candidate configuration without requiring a commit.

Answer

delete configuration

Answer

load override

Answer

rollback 1

Question 3

A Juniper device is experiencing high CPU utilization due to a routing protocol process. The engineer suspects a specific BGP peer is causing the issue. Which operational command can be used to collect diagnostic information about the routing protocol processes?

Accepted Answer

show system processes extensive. 'show system processes extensive' displays detailed CPU and memory usage for each individual process, including routing protocol daemons like bgpd. This allows the engineer to see which routing protocol process (e.g., bgpd) is consuming excessive CPU resources. However, it does not identify a specific BGP peer; further investigation with commands like 'show bgp neighbor' would be needed to isolate the peer.

Answer

request support information

Answer

show bgp summary

Answer

monitor traffic interface

Question 4

An engineer needs to view the current active configuration on a Juniper device. Which command will display the configuration that is currently running?

Accepted Answer

show configuration. The 'show configuration' command displays the current active configuration that is committed and running on a Juniper device. Unlike Cisco's 'show running-config', Junos uses a commit model where the candidate configuration is activated only after a 'commit' operation, and 'show configuration' shows that committed, active configuration.

Answer

show chassis hardware

Answer

show interfaces terse

Answer

show system commit

Question 5

During a maintenance window, an engineer needs to apply a series of configuration changes that are stored in a text file. Which command sequence should be used to load and apply the changes from the file?

Accepted Answer

configure; load merge /var/tmp/changes.txt; commit. The engineer needs to enter configuration mode (configure) and then use the 'load merge' command to merge the contents of the text file into the candidate configuration without replacing the entire configuration. The 'commit' command then activates the changes. This is the standard Junos workflow for applying incremental changes from a file.

Answer

request system configuration rescue save

Answer

load override /var/tmp/changes.txt; commit

Answer

configure; load patch /var/tmp/changes.txt; commit

Question 6

An engineer notices that a Juniper device is not saving configuration changes across reboots. What is the most likely cause?

Accepted Answer

The candidate configuration was not committed.. In Junos OS, configuration changes are stored in a candidate configuration and only become active and persistent across reboots after a 'commit' operation. Without a commit, the changes remain in the candidate buffer and are discarded upon reboot, causing the device to revert to the last committed configuration.

Answer

The rescue configuration is not set.

Answer

The device is booting from factory-default configuration.

Answer

The command 'request system reboot' was used instead of 'commit'.

Question 7

Which TWO statements are true about the Junos OS candidate configuration model? (Choose two.)

Accepted Answer

The candidate configuration can be modified without affecting the active configuration.. The Junos OS candidate configuration model allows modifications to be made to a separate candidate configuration file without affecting the active configuration currently running on the device. This ensures that changes can be staged, reviewed, and validated before being committed, providing a safe and non-disruptive way to manage configuration changes.

Answer

Each change is applied incrementally to the active configuration.

Answer

The candidate configuration is stored in a separate file from the active configuration.

Answer

After a commit, the candidate configuration is automatically discarded.

Question 8

Which THREE commands are valid Junos operational mode commands for monitoring network diagnostics? (Choose three.)

Accepted Answer

traceroute. The 'traceroute' command in Junos operational mode sends a series of UDP packets with increasing TTL values to discover the path a packet takes to a destination, which is a standard network diagnostic tool. It is a valid operational mode command used for monitoring network connectivity and path analysis.

Answer

show configuration

Answer

request system reboot

Question 9

Which TWO statements correctly describe the function of the 'commit' command in Junos OS? (Choose two.)

Accepted Answer

It validates the candidate configuration for syntax errors.. The 'commit' command in Junos OS first validates the candidate configuration for syntax errors before applying it. If syntax errors are found, the commit fails and the candidate configuration is not applied, ensuring the device does not enter an inconsistent state. This validation step is a core part of Junos's transactional configuration model, where changes are staged in a candidate configuration and then committed atomically.

Answer

It schedules the configuration to be applied at a later time.

Answer

It discards the candidate configuration after saving.

Answer

It automatically reboots the device to apply the changes.

Question 10

Based on the exhibit, what is the most likely reason for the ping failure?

Accepted Answer

The neighbor device is not configured or is unreachable.. The ping failure is most likely due to the neighbor device not being configured or unreachable because the output shows the interface is up (Physical link is Up) and the unit is enabled (Unit 0 is enabled), but there is no neighbor discovery or ARP entry. Without a valid next-hop or neighbor reachability, ICMP echo requests cannot be forwarded, resulting in ping failure.

Answer

A firewall filter is blocking ICMP traffic.

Answer

The interface is disabled at the unit level.

Answer

The interface is administratively down.