JN0-106 Practice Test 24 — 15 Questions

Question 1

A network engineer is troubleshooting connectivity between two hosts on the same VLAN connected to different Juniper EX switches. The MAC address table on each switch shows the correct MAC addresses for both hosts, but ping fails. What is the most likely cause?

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

Accepted Answer

The hosts are configured with IP addresses in different subnets. Since both switches have correctly learned the MAC addresses of both hosts, Layer 2 forwarding across the trunk is working, meaning the VLAN is allowed. The ping failure therefore points to a Layer 3 issue: the hosts are configured with IP addresses in different subnets. They cannot communicate via IP without a router, even though they are on the same VLAN. The correct answer is B.

Answer

The VLAN is not allowed on the trunk between the switches

Answer

The ARP cache on the hosts is stale

Answer

Spanning Tree Protocol is blocking a port

Question 2

A network administrator configures a static route on a Juniper device: `set routing-options static route 192.168.100.0/24 next-hop 10.0.0.1`. The administrator verifies the route is present in the routing table but notices it is not active. What is the most likely cause?

Accepted Answer

The next-hop address 10.0.0.1 is not reachable.. A static route becomes active only if the next-hop address is reachable via a directly connected or active route in the routing table. Since the administrator verified the route is present but not active, the most likely cause is that the next-hop 10.0.0.1 is not reachable (e.g., no ARP resolution or no interface with that subnet). Junos marks such routes as hidden or inactive until the next hop is reachable.

Answer

The route is not committed.

Answer

The preference of the static route is higher than 15.

Answer

The destination prefix is already learned via OSPF with a lower metric.

Question 3

A junior administrator wants to discard all uncommitted changes made in the current configuration session. Which command accomplishes this?

Accepted Answer

rollback 0. The `rollback 0` command reverts the candidate configuration to the active committed configuration, effectively discarding all uncommitted changes made during the current session. In Junos, configuration changes are stored in a candidate configuration until explicitly committed; `rollback 0` loads the last committed configuration (index 0) into the candidate, wiping out any uncommitted edits.

Answer

commit check

Answer

load factory-default

Answer

clear configuration

Question 4

An administrator is configuring a static route to a remote network 10.10.10.0/24 via next-hop 192.168.1.1. Which command correctly adds this route?

Accepted Answer

set routing-options static route 10.10.10.0/24 next-hop 192.168.1.1. The Junos syntax for configuring a static route uses the hierarchy `set routing-options static route next-hop

`. The prefix must include the subnet mask in CIDR notation (e.g., /24). This command installs a route to 10.10.10.0/24 with next-hop 192.168.1.1 into the routing table.

Answer

set routing-options route 10.10.10.0/24 static next-hop 192.168.1.1

Answer

set routing-options static route 10.10.10.0 next-hop 192.168.1.1 mask 255.255.255.0

Answer

set routing-options static next-hop 192.168.1.1

Question 5

An engineer needs to configure a static route on a Juniper device. Which statement is true regarding the configuration process?

Accepted Answer

Configuration changes must be committed to become active.. In Junos, configuration changes are made in a candidate configuration and do not take effect until explicitly committed using the 'commit' command. This two-phase model (edit then commit) ensures that changes are validated before activation, preventing partial or incorrect configurations from disrupting network operations. Option B correctly identifies this requirement.

Answer

The set command activates the change for 10 minutes by default.

Answer

The configuration is immediately active upon entering the set command.

Answer

The commit command requires a reboot to take effect.

Question 6

An administrator needs to change a portion of the configuration by matching a pattern and replacing it with new text. Which Junos configuration mode command should be used?

Accepted Answer

replace pattern. The 'replace pattern' command in Junos configuration mode allows an administrator to search for a specific text pattern using regular expressions and replace it with new text. This is the correct command for pattern-based substitution within the configuration hierarchy, as it directly matches and replaces text without requiring manual deletion or re-entry.

Answer

rename

Answer

copy

Answer

set replace pattern

Question 7

A technician is troubleshooting a connectivity issue and needs to see the path packets take to a remote host. Which Junos command is appropriate?

Accepted Answer

traceroute. The `traceroute` command in Junos is the correct tool for tracing the path packets take to a remote host. It sends UDP probes with increasing TTL values and listens for ICMP Time Exceeded messages from intermediate routers, revealing each hop along the route. This directly matches the technician's need to see the path packets take.

Answer

monitor interface

Answer

ping

Answer

show route

Question 8

An engineer has modified the configuration and wants to apply changes but also wants to verify that the changes are syntactically correct before committing. What command should the engineer use?

Accepted Answer

commit check. The `commit check` command validates the candidate configuration for syntax errors without activating it. This allows the engineer to verify that the changes are syntactically correct before committing, ensuring the configuration is valid and reducing the risk of committing a broken configuration.

Answer

rollback

Answer

commit confirmed

Answer

commit

Question 9

A network engineer needs to check the system's disk space usage. Which command should be used?

Accepted Answer

show system storage. The 'show system storage' command displays disk space usage on Junos devices, including total, used, and available space for each mounted filesystem. This is the correct command for monitoring storage utilization, as it directly reports on the /, /config, and /var partitions critical for system operation.

Answer

show configuration

Answer

show version

Answer

show system uptime

Question 10

A junior administrator is told to implement configuration changes that must survive a reboot. Which statement is correct?

Accepted Answer

Performing a 'commit' saves the active configuration to non-volatile storage.. In Junos, the 'commit' command activates the candidate configuration and saves it to non-volatile storage (the /config directory on the flash drive), ensuring it survives a reboot. This is the standard method for making configuration changes persistent across system restarts.

Answer

The 'commit confirmed' command ensures persistence.

Answer

Changes made using 'set' commands are automatically saved to the startup config.

Answer

The 'commit' command only writes to RAM, so a 'request system configuration save' is needed.

Question 11

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 12

Refer to the exhibit. Which filesystem should the administrator investigate to free up disk space?

Accepted Answer

/var. The /var filesystem on Junos devices stores system logs, core dumps, and temporary files. When disk space is low, /var is the most common culprit because it contains rotating log files (e.g., messages, interactive-commands) and crash data that can accumulate rapidly. The administrator should investigate /var to free up space by clearing old logs or core files.

Answer

/config

Answer

/ (root)

Answer

/dev

Question 13

An administrator needs to see which interfaces are configured and their current operational status in a concise format. Which command provides this information?

Accepted Answer

show interfaces terse. The 'show interfaces terse' command displays a concise, table-like output listing all interfaces (including logical units) along with their administrative status (up/down) and operational status (up/down). This is the most efficient way to see both configured interfaces and their current state in a compact format, as required by the question.

Answer

show interfaces

Answer

show configuration interfaces

Answer

show interfaces descriptions

Question 14

A network administrator needs to remove all configuration changes made since the last commit without affecting the current active configuration. Which command should be used?

Accepted Answer

rollback 0. The `rollback 0` command reverts the candidate configuration to the currently active committed configuration, discarding all uncommitted changes without affecting the active configuration. This is the correct way to undo all modifications made since the last commit while keeping the running configuration intact.

Answer

rollback 1

Answer

deactivate

Answer

delete

Question 15

After upgrading Junos, a router fails to boot with a file system error. The admin needs to recover the system from the backup partition. Which key should be pressed during boot to access the boot menu?

Accepted Answer

Space. Pressing the Space bar during the boot process on a Juniper device interrupts the normal boot sequence and presents the boot menu. From this menu, the administrator can select the backup Junos partition (typically labeled as '1' or 'backup') to recover the system when the primary partition has a file system error.

Answer

Ctrl+C

Answer

Esc

Answer

Enter