JNCIA-JUNOS Junos OS Fundamentals Practice Test 2 — 15 Questions

Question 1

A network engineer notices that a Junos device is not forwarding traffic for a specific subnet. The routing table shows the route for that subnet, but traffic is still not being forwarded. Which command should the engineer use to verify whether the firewall filter is dropping the traffic?

Accepted Answer

show firewall filter log. Option D is correct because the 'show firewall filter log' command displays the log entries generated by firewall filter terms that have a 'log' action configured. When traffic is not being forwarded despite a valid route, a firewall filter may be silently dropping packets; this command reveals which packets matched the filter and whether they were logged, helping to identify drops.

Answer

show interfaces terse

Answer

show firewall filter counter

Answer

show firewall filter

Question 2

Which THREE of the following statements are true regarding Junos OS commit operations?

Accepted Answer

The 'commit check' command validates the candidate configuration without activating it.. Option A is correct because the 'commit check' command validates the candidate configuration for syntax and semantic errors without activating it. This allows an administrator to verify changes before making them active, preventing potential misconfigurations from disrupting network operations.

Answer

You can run multiple commit scripts during a single commit operation.

Answer

The rollback command reverts to the current active configuration.

Question 3

Refer to the exhibit. An engineer wants to verify that static routes for 10.0.1.0/24 and 10.0.2.0/24 are present in the routing table. Based on the output, which statement is true?

Accepted Answer

Both routes are active and have the same preference value.. The output shows both 10.0.1.0/24 and 10.0.2.0/24 as static routes with a preference of 5. Since the preference value is the same and both are listed as active (the 'A' flag is present in the routing table), both routes are installed and active in the forwarding table. In Junos, a static route's default preference is 5, and any route with a lower preference is preferred; here both have equal preference, so they coexist as active routes.

Answer

Both routes have a preference of 0.

Answer

Only the 10.0.1.0/24 route is active.

Answer

Both routes use the same next-hop IP address.

Question 4

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?

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.. Option C is correct because 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 5

A network engineer needs to check the operational status of all interfaces on a Juniper device. Which command provides a summary of interface status including link state, protocol state, and error counters?

Accepted Answer

show interfaces terse. Option C is correct because the 'show interfaces terse' command provides a concise summary of all interfaces, displaying the interface name, administrative status (Admin), link state (Link), protocol state (Proto), and a brief description. This command is specifically designed for a quick operational overview, including error counters in the full output when combined with other flags, but the terse output itself focuses on status and protocol state, which directly meets the engineer's requirement.

Answer

show interfaces

Answer

show configuration interfaces

Answer

show interface descriptions

Question 6

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.. Option B is correct because 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 7

Refer to the exhibit. How many next hops are configured for the 192.168.1.0/24 route?

Accepted Answer

2. The correct answer is D because the route 192.168.1.0/24 has two next hops configured: one via 10.0.0.2 and another via 10.0.0.3. This is a case of equal-cost multipath (ECMP) routing, where Junos installs multiple next hops for the same prefix to load-balance traffic across multiple paths.

Answer

0

Answer

3

Answer

1

Question 8

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

Question 9

Match each Junos file system directory to its content.

Question 10

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 11

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 12

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 13

Which command displays the current hostname of a Junos device?

Accepted Answer

show system host-name. The command 'show system host-name' is the correct operational mode command to display the current hostname configured on a Junos device. It retrieves the hostname from the active configuration and displays it in the output, confirming the device's identity on the network.

Answer

show chassis hardware

Answer

show configuration system host-name

Answer

show system uptime

Question 14

An administrator needs to grant a user read-only access to the device via SSH. Which configuration should be applied?

Accepted Answer

set system login user guest class read-only. Option B is correct because the 'read-only' class in Junos provides exactly the required level of access: users can view configuration and operational data but cannot make any changes. The 'set system login user guest class read-only' command assigns the predefined 'read-only' login class to the user 'guest', which permits SSH login with read-only privileges. This matches the administrator's requirement precisely.

Answer

set system login user admin class operator

Answer

set system login user readonly class super-user

Answer

set system login user guest class operator

Question 15

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'. Option D is correct because 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