JN0-106 Practice Test 25 — 15 Questions

Question 1

A technician is troubleshooting a routing issue and needs to see real-time updates of BGP prefixes being received. Which command should be used?

Accepted Answer

monitor route bgp. The 'monitor route bgp' command in Junos OS provides a real-time, continuously updated view of BGP routes as they are learned or withdrawn. Unlike static show commands, this monitor command refreshes the output dynamically, making it ideal for observing live BGP prefix updates during troubleshooting.

Answer

monitor traffic interface ge-0/0/0

Answer

show route advertising-protocol bgp

Answer

show route protocol bgp

Question 2

A network administrator has made several configuration changes and now wants to revert all uncommitted changes back to the last committed configuration. Which command should they use?

Accepted Answer

rollback 0. The 'rollback 0' command reverts all uncommitted changes and restores the active configuration to the last committed configuration. In Junos, candidate configurations are stored in numbered rollback slots (0 being the most recent committed configuration), so 'rollback 0' discards any uncommitted edits and loads the last committed state.

Answer

rollback 1

Answer

load override terminal

Answer

commit check

Question 3

An administrator is troubleshooting an interface and wants to see real-time packet statistics. Which command should they use?

Accepted Answer

monitor interface. The 'monitor interface' command in Junos provides real-time, continuously updated packet statistics for a specified interface, making it the correct choice for live troubleshooting. Unlike static commands, it refreshes statistics every second until interrupted, allowing the administrator to observe traffic patterns as they occur.

Answer

traceoptions

Answer

show interfaces statistics

Answer

show interfaces extensive

Question 4

Two routers are connected via a point-to-point Ethernet link. They are configured with IP addresses in the same subnet, but OSPF does not form an adjacency. The link is up/up. What is a likely cause?

Accepted Answer

The OSPF hello and dead intervals are mismatched. OSPF requires that Hello and Dead intervals match between neighbors on a point-to-point link to form an adjacency. Even though the link is up/up and IP addresses are in the same subnet, mismatched timers prevent the routers from agreeing on neighbor state, so no adjacency forms.

Answer

The routers are in different OSPF areas

Answer

OSPF authentication is configured on one router but not the other

Answer

The routers have the same router ID

Question 5

A junior network engineer is learning JunOS CLI and wants to view the last 10 lines of the system log file. They log into the device and type 'show log messages | last 10'. They receive an error: 'unknown pipe command'. Which pipe command should they use instead?

Accepted Answer

| tail 10. In JunOS CLI, the pipe command to display the last N lines of output is '| tail N', not '| last N'. The 'tail' command filters the output to show only the final lines, analogous to the Unix 'tail' utility. Option D is correct because '| tail 10' will show the last 10 lines of the system log file.

Answer

| last 10

Answer

| display 10

Answer

| head 10

Question 6

During a maintenance window, an engineer needs to apply a configuration change that reverts automatically if the commit fails or the administrator does not confirm within a set time. Which feature should be used?

Accepted Answer

commit confirmed. The 'commit confirmed' feature allows an engineer to apply a configuration change that automatically reverts to the previous configuration if the commit is not confirmed within a specified time period (default 10 minutes). This ensures that if the commit fails or the administrator loses connectivity, the system rolls back safely without manual intervention.

Answer

commit check

Answer

commit synchronize

Answer

commit at 03:00

Question 7

An engineer observes that traffic destined to 203.0.113.0/24 is being load-balanced across two equal-cost paths via OSPF. The engineer wants to ensure that all traffic for this prefix uses only one path unless the primary path fails. Which configuration change should be made?

Accepted Answer

Set the OSPF metric on the backup interface to a higher value.. Increasing the OSPF metric on the backup interface makes that path less preferred in the SPF calculation, breaking the equal-cost multipath (ECMP) condition. OSPF selects routes based on the lowest metric; by raising the metric on one interface, the engineer ensures only the lower-metric path is used for forwarding, with automatic failover to the backup path if the primary fails.

Answer

Configure a static route for 203.0.113.0/24 with a lower preference.

Answer

Use policy-options to set a higher preference for one of the paths.

Answer

Modify the load-balance configuration under forwarding-options.

Question 8

A network engineer needs to revert to the configuration that was committed two commits ago. Which rollback number should they use?

Accepted Answer

rollback 2. The rollback command in Junos OS allows reverting to a previously committed configuration. The rollback number corresponds to the number of commits ago, starting with rollback 0 for the most recent commit, rollback 1 for the commit before that, and so on. Therefore, to revert to the configuration committed two commits ago, the correct rollback number is 2.

Answer

rollback 0

Answer

rollback 1

Answer

rollback 3

Question 9

A Juniper router is configured with two static routes to the same destination network, both with the same preference. One route has a metric of 5, the other a metric of 10. Which route will be installed in the routing table?

Accepted Answer

The route with metric 5 is installed. In JUNOS, when multiple static routes to the same destination have the same preference (administrative distance), the route with the lower metric is selected for installation in the routing table. Here, metric 5 is lower than metric 10, so the route with metric 5 is installed. This behavior follows the standard route selection process where preference is evaluated first, then metric (also called cost or next-hop metric) as a tiebreaker.

Answer

Neither route is installed because they conflict

Answer

The route with metric 10 is installed

Answer

Both routes are installed with equal preference

Question 10

An engineer is editing the candidate configuration on a Junos device and wants to verify the changes she has made so far without leaving configuration mode or committing anything. She also needs to see only the lines she has added or modified relative to the active configuration. Which command accomplishes this?

Accepted Answer

show | compare. The compare pipe in configuration mode shows the delta between the candidate and active configurations, marking additions and deletions. It is the standard way to preview pending edits before a commit, working entirely within configuration mode. Commands that render the whole candidate, validate syntax, or revert the candidate do not satisfy the need to see only modified lines.

Answer

show configuration | display set

Answer

commit check

Answer

rollback 0

Question 11

An engineer is preparing a Juniper EX Series switch for deployment and wants to load a previously saved configuration from a USB device into the candidate configuration without deleting any existing candidate statements. The saved file is named ex-config.conf and is located in the /var/tmp directory. Which command accomplishes this?

Accepted Answer

load merge /var/tmp/ex-config.conf. The load merge command is designed to combine a saved configuration file with the current candidate configuration, keeping all existing candidate statements intact. The requirement is to add the saved configuration without deleting anything, so merge is the correct action. Other load variants either replace hierarchies, override the entire candidate, or expect a different file format.

Answer

load set /var/tmp/ex-config.conf

Answer

load override /var/tmp/ex-config.conf

Answer

load replace /var/tmp/ex-config.conf

Question 12

A network engineer is configuring a new Juniper SRX Series firewall and wants to verify the configuration before committing it. The engineer wants to check the syntax and semantic validity of the candidate configuration without activating it. Which command should the engineer use?

Accepted Answer

commit check. The commit check command is specifically designed to validate the candidate configuration for errors without committing it. It performs the same validation as a commit but stops short of activating the changes. This allows the engineer to ensure the configuration is correct before applying it to the device.

Answer

show | compare

Answer

commit confirmed

Answer

commit

Question 13

You are configuring a Juniper EX Series switch port that connects to an IP phone. The phone must tag its voice traffic in VLAN 30, while an attached PC sends untagged traffic that should be placed in VLAN 20. You want to configure the port so that both traffic types are accepted on the same physical interface. Which port mode should you configure?

Accepted Answer

trunk mode with native-vlan-id 20 and VLAN 30 as a member. A trunk port can carry multiple VLANs, with the native VLAN handling untagged frames and other VLANs handling tagged frames. Setting the native VLAN to 20 places untagged PC traffic correctly, while including VLAN 30 as a member allows the phone's tagged voice traffic. This is the correct way to support both devices on one switch port.

Answer

access mode with vlan-id 30

Answer

trunk mode with native-vlan-id 20

Answer

access mode with vlan-id 20

Question 14

An administrator is logged into a Juniper EX Series switch in configuration mode and wants to verify how the device will interpret a specific interface configuration before applying it. Which operational-mode command should the administrator use to validate the candidate configuration for syntax and semantic errors without committing it?

Accepted Answer

commit check. The commit check command validates the candidate configuration for syntax and semantic errors without committing it, which is exactly what the administrator needs before applying interface changes. The other commands either apply changes or only show differences, so they do not provide a safe validation step. Using commit check ensures the configuration is correct before it becomes active.

Answer

commit confirmed

Answer

show | compare

Answer

load override

Question 15

A network administrator needs to check the current software version and hardware model of a Juniper device. Which command should the administrator use?

Accepted Answer

show version. The show version command is specifically designed to display the Junos OS software version and hardware model. It provides a concise summary that includes the hostname, model, Junos version, and uptime. The other commands either focus on hardware details or are invalid, making show version the correct choice for this scenario.

Answer

show system information

Answer

show configuration version

Answer

show chassis hardware