JN0-106 Junos OS Fundamentals Practice Test 5 — 15 Questions

Question 1

You are administering a Juniper MX240 router that provides connectivity to multiple customer sites. The router uses BGP to exchange routes with two upstream ISPs. Recently, you applied a new firewall filter to the loopback interface to restrict management access. After committing the configuration, you can no longer establish SSH sessions to the router from the management network. You are currently connected via console. The loopback filter is still applied. You suspect the filter is blocking SSH traffic from the management network. What should you do to restore SSH access without losing the other filter rules?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Add a new term at the beginning of the filter that accepts SSH traffic from the management network, then reorder the terms so that this term is evaluated first.. Firewall filters in Junos are evaluated in order, and adding a term at the beginning that explicitly accepts SSH traffic from the management network ensures that the SSH packets are permitted before any subsequent deny terms are evaluated. This preserves all existing filter rules while restoring SSH access. The 'insert' command or reordering terms is necessary to place the new term first, as the default behavior appends new terms to the end of the filter.

Answer

Roll back to the previous configuration using 'rollback 0' and commit.

Answer

Add a new term at the end of the filter that accepts SSH traffic from any source.

Answer

Delete the firewall filter from the loopback interface and commit.

Question 2

Which THREE statements are true about commit operations in Junos OS?

Accepted Answer

Multiple users can make configuration changes simultaneously, but only one can commit at a time.. Junos OS allows multiple users to enter configuration mode and make changes simultaneously, but the commit operation is serialized: only one user can commit at a time. This prevents conflicting changes from being applied concurrently, ensuring configuration consistency.

Answer

The 'commit confirmed' command immediately discards changes if not confirmed.

Answer

The 'commit' command always requires 'commit synchronize' when using dual Routing Engines.

Question 3

Order the steps to configure a user account with a password in Junos.

Accepted Answer

Set the class (set system login user class ), then set the authentication method to plain-text-password (set system login user authentication plain-text-password), then commit the configuration.. The correct order to configure a user account in Junos involves setting both the class and authentication before committing. Options A and B are both valid sequences because the order of setting the class and authentication does not matter; the configuration is applied only upon commit. Option C is wrong because committing before setting the authentication leaves the user without a password. Option D is wrong because committing before setting the class results in an incomplete user configuration with no privilege level.

Answer

Set the class, commit the configuration, then set the authentication method to plain-text-password.

Answer

Set the authentication method to plain-text-password, commit the configuration, then set the class.

Question 4

Which Junos CLI mode allows a user to view the configuration and execute operational commands, but not make configuration changes?

Accepted Answer

Operational mode. In Junos OS, Operational mode (indicated by the `>` prompt) allows users to execute operational commands (e.g., `show`, `ping`, `traceroute`) and view the active configuration using `show configuration`, but it does not permit any changes to the configuration. Configuration changes require entering Configuration mode (indicated by the `#` prompt) via the `configure` command. This separation enforces a strict two-tier access model, ensuring that operational tasks do not inadvertently alter the device's configuration.

Answer

Monitor mode

Answer

Enable mode

Answer

Configuration mode

Question 5

A network administrator makes several changes to the configuration but decides to discard all uncommitted changes and start fresh. Which command should be used to revert the candidate configuration back to the current active configuration?

Accepted Answer

rollback 0. The 'rollback 0' command reverts the candidate configuration to the currently active configuration, discarding all uncommitted changes. This is because Junos maintains a rollback database of the last 50 committed configurations, with index 0 always representing the active configuration. Using 'rollback 0' effectively resets the candidate configuration to match the active one, allowing the administrator to start fresh without affecting the running system.

Answer

load override

Answer

commit check

Answer

rollback 1

Question 6

A Juniper device fails to boot and stops at the 'loader>' prompt. What is the most likely cause of this issue?

Accepted Answer

Bad boot device or missing kernel. When a Juniper device stops at the 'loader>' prompt, it indicates that the boot process has failed to locate or load the kernel (juniper-kernel) from the boot device (e.g., internal flash, USB, or hard disk). This is typically caused by a corrupted boot device, missing kernel image, or incorrect boot device selection in the boot loader (UBoot or CFE). The loader prompt is a low-level environment used for recovery, not a sign of configuration or authentication issues.

Answer

Corrupted configuration file

Answer

Hardware failure of the power supply

Answer

Missing root password

Question 7

A technician notices that the /var partition on a Junos device is 95% full. Which action will immediately free up disk space without affecting device operation?

Accepted Answer

Clear log files using 'clear log messages'. The 'clear log messages' command immediately removes the contents of the active log files (e.g., messages, interactive-commands) without requiring a reboot or affecting running processes. This directly frees up space in /var/log, which is a primary consumer of the /var partition, while leaving the directory structure intact so logging continues normally.

Answer

Delete unused software packages using 'request system software delete'

Answer

Reboot the device

Answer

Remove the /var/log directory

Question 8

A network operator needs to backup the current configuration to a file on the local flash. Which command accomplishes this?

Accepted Answer

show configuration | save /var/tmp/backup.conf. The correct command to backup the current configuration from operational mode is `show configuration | save /var/tmp/backup.conf`. This pipes the active configuration to the save command, writing it to the specified file. Option B (`save /var/tmp/backup.conf`) is a configuration mode command and will not work in operational mode. Option A saves the rescue configuration, not the active configuration. Option C commits the configuration and exits but does not save to a file.

Answer

request system configuration rescue save

Answer

save /var/tmp/backup.conf

Answer

commit and-quit

Question 9

Refer to the exhibit. The network administrator made a change that caused connectivity loss. They need to revert to the configuration before the most recent commit. Which command would accomplish this?

Accepted Answer

rollback 1. In Junos, rollback numbers are stored with 0 being the most recent committed configuration. To revert to the configuration before the most recent commit, you need to load the configuration that was active before that change. That is rollback 1, which represents the second most recent commit. Using rollback 0 would load the configuration that caused the issue, not fix it.

Answer

rollback 0

Answer

rollback 3

Answer

rollback 2

Question 10

What is the primary function of the fxp0 interface on a Juniper device?

Accepted Answer

Management interface. The fxp0 interface is a dedicated out-of-band management Ethernet port on Juniper devices, used exclusively for management traffic such as SSH, SNMP, and syslog. It is separate from the data plane and control plane forwarding interfaces, ensuring administrative access remains available even if the routing or forwarding planes are disrupted.

Answer

Internal routing

Answer

Loopback testing

Answer

Data plane forwarding

Question 11

An engineer wants to roll back to the previous configuration. Which command should be used?

Accepted Answer

rollback 1. The `rollback 1` command loads the previous committed configuration (the configuration before the last commit) into the candidate configuration, discarding any uncommitted changes. This allows the engineer to replace the current candidate with the desired historical configuration. In Junos, `rollback 0` loads the most recently committed configuration (the current active configuration), not the previous one.

Answer

delete

Answer

rollback 0

Answer

commit check

Question 12

A Junos device has multiple configuration files saved. Which command shows the available rollback configurations?

Accepted Answer

show system commit. The 'show system commit' command displays a list of all committed configuration revisions, including their commit IDs and timestamps, which are used to roll back to a previous configuration. The rollback feature in Junos relies on these stored commit files, and the command explicitly shows the available rollback points.

Answer

show system configuration

Answer

show system rollback

Answer

show configuration | display rollback

Question 13

What happens when a user issues the 'request system reboot' command without any options?

Accepted Answer

The device prompts for confirmation.. When a user issues the 'request system reboot' command without any options, Junos OS prompts for confirmation before proceeding. This is a safety mechanism to prevent accidental reboots, as the command does not automatically reboot the device immediately or schedule a delayed reboot by default.

Answer

The device reboots after the current commit.

Answer

The device reboots immediately.

Answer

The device schedules a reboot in 5 minutes.

Question 14

Which TWO statements are true about the Junos file system? (Choose two.)

Accepted Answer

The /config directory contains configuration files.. The /config directory in the Junos file system stores the active and backup configuration files, including juniper.conf and juniper.conf.gz. These files are critical for device operation and are loaded during the boot process.

Answer

The /altroot directory is a backup root filesystem.

Answer

The /kernel directory contains the operating system kernel.

Answer

The root directory (/) is a RAM disk.

Question 15

Which TWO statements describe correct methods to enter configuration mode? (Choose two.)

Accepted Answer

Type 'edit' at the operational mode prompt.. The 'edit' command transitions from operational mode into configuration mode. Option B is correct because the 'configure exclusive' command enters configuration mode in exclusive mode, which is a valid method. Option C is correct because the 'configure' command enters configuration mode in shared mode. Options D and E are invalid commands in Junos OS.

Answer

Type 'cli' at the operational mode prompt.

Answer

Type 'expert' at the operational mode prompt.