JN0-106 Practice Test 11 — 15 Questions

Question 1

You are managing a Juniper MX router that serves as a BGP route reflector for multiple customer VPNs. The router has two routing engines (RE0 and RE1) in a graceful switchover (GRES) configuration. During a routine maintenance window, you need to upgrade the Junos OS from version 18.1R1 to 20.2R2. The upgrade must minimize traffic disruption. You have already staged the new image on both REs. Which sequence of commands ensures minimal impact?

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

Accepted Answer

On RE1: request system software add jinstall-20.2R2.tgz reboot; after reboot, on RE0: request chassis routing-engine master switch; then request system software add jinstall-20.2R2.tgz reboot. It performs a non-disruptive upgrade by first upgrading the backup RE (RE1), then switching mastership to the upgraded RE, and finally upgrading the original master RE. This sequence leverages Graceful Routing Engine Switchover (GRES) to maintain BGP sessions and VPN forwarding during the upgrade, minimizing traffic disruption.

Answer

On RE0: request system software add jinstall-20.2R2.tgz reboot; then on RE1 same command

Answer

On RE0: request system reboot (without adding software)

Answer

On both REs: request system software add jinstall-20.2R2.tgz reboot

Question 2

Which TWO statements about configuration archival in Junos are true?

Accepted Answer

The 'system archival' hierarchy enables automatic backup of configurations.. The 'system archival' hierarchy in Junos is specifically designed to enable automatic backup of configuration files. This feature allows administrators to configure periodic transfers of committed configurations to a remote server, ensuring configuration history is preserved without manual intervention.

Answer

Archival stores the candidate configuration.

Answer

Archival only saves the rescue configuration.

Answer

Archival automatically archives after every commit without any configuration.

Question 3

Which THREE modes can be used to enter configuration mode in Junos? (Choose three.)

Accepted Answer

configure private. 'configure private' creates a private configuration session that isolates candidate changes from other users, allowing multiple users to stage changes simultaneously without interference. This mode is one of the three standard configuration modes in Junos, alongside exclusive and shared.

Answer

configure static

Answer

configure dynamic

Question 4

Refer to the exhibit. Why is the static route not active?

Accepted Answer

The static route has a higher preference than the OSPF route.. Junos uses route preference (administrative distance) to select the active route when multiple routes to the same destination exist. By default, OSPF has a preference of 10, while a static route has a preference of 5. Since a lower preference value is more preferred, the static route should normally be active. However, the question indicates the static route is not active, which implies the static route's preference has been manually set higher than OSPF's preference (e.g., static route preference > 10), causing OSPF to be selected as the active route.

Answer

The OSPF route has a lower metric.

Answer

The static route's next-hop is not reachable.

Answer

The static route is not committed.

Question 5

A network engineer accidentally committed a configuration on a Juniper router that caused a loss of management access via SSH and SNMP. The engineer has console access and the device is still operational. Before the change, the engineer had saved a rescue configuration using 'request system configuration rescue save'. Which action should the engineer take to restore management access most quickly?

Accepted Answer

At the shell prompt, execute 'cli -c "rollback rescue"' and then commit.. The 'request system configuration rescue save' command stores a rescue configuration that can be rolled back to using 'rollback rescue' in configuration mode. Since the engineer has console access, they can enter configuration mode and execute 'rollback rescue' followed by 'commit' to instantly revert to the last known working configuration, restoring SSH and SNMP access without requiring a reboot.

Answer

At the configuration mode, execute 'rollback 0'.

Answer

Power cycle the device; it will automatically boot with the rescue configuration.

Answer

Reboot the device and press the space bar to load the rescue configuration.

Question 6

An engineer wants to revert all uncommitted changes in the candidate configuration and start fresh from the currently active configuration. Which command should be used?

Accepted Answer

rollback 0. The `rollback 0` command reverts all uncommitted changes in the candidate configuration and restores it to match the currently active configuration (the one most recently committed). This is because Junos stores the last 50 committed configurations, with index 0 always representing the active configuration. Using `rollback 0` effectively discards any uncommitted edits and starts fresh from the last committed state.

Answer

commit check

Answer

rollback 1

Answer

load override terminal

Question 7

Which TWO statements about configuration storage in Junos are true?

Accepted Answer

The rescue configuration is stored in /config/rescue.conf.gz.. The rescue configuration is stored as a compressed file at /config/rescue.conf.gz on Junos devices. This configuration is saved using the 'request system configuration rescue save' command and can be loaded with 'rollback rescue' to recover from a configuration that prevents the device from booting properly.

Answer

The rollback configurations are stored in /config/juniper.conf.0.gz, .1.gz, etc.

Answer

The candidate configuration is stored in /config/.

Answer

The factory default configuration is stored in /etc/config/.

Question 8

A network operator needs to upgrade the Junos OS on the backup RE (re1) of a dual-RE system. Which procedure ensures that only the backup RE is upgraded and rebooted without affecting the forwarding plane?

Accepted Answer

Use 'request system software add re1' and then 'request system reboot re1'. The 'request system software add re1' command installs the Junos OS image only on the backup Routing Engine (RE1), and the subsequent 'request system reboot re1' reboots only that RE. In a dual-RE system, this procedure isolates the upgrade to the backup RE, ensuring the forwarding plane remains active on the primary RE (RE0) and no traffic disruption occurs.

Answer

Use 'request system software add <image> both' and then 'request system reboot both'

Answer

Use 'request system software add <image> re0' and then 'request system reboot re0'

Answer

Copy the image to both REs and reboot the backup RE with 'request system reboot slice 1'

Question 9

Refer to the exhibit. Based on the log messages, what is the most likely cause of the interface flapping?

Accepted Answer

Faulty SFP module. The log messages show repeated link up/down events (interface flapping). In Junos, interface flapping is most commonly caused by a faulty SFP module, as physical layer issues like degraded optics or loose connections trigger continuous link transitions. The logs typically show 'link up' followed by 'link down' without any protocol-level errors, pointing to a hardware fault rather than configuration mismatches.

Answer

MTU mismatch

Answer

Duplicate IP address

Answer

Spanning tree topology change

Question 10

A router has two routes to the same destination: one with preference 10 and metric 5, and another with preference 15 and metric 3. Which route will be installed in the forwarding table?

Accepted Answer

The route with preference 10.. In Junos, the route preference (administrative distance) is the primary criterion for selecting the best route to a destination. The route with preference 10 is preferred over the route with preference 15, regardless of metric values. The route with preference 10 is installed in the forwarding table.

Answer

The route with metric 3.

Answer

Neither route is installed.

Answer

Both routes are installed if ECMP is enabled.

Question 11

A Juniper device has multiple candidate configurations loaded. The administrator wants to discard all uncommitted changes and revert to the last committed configuration. Which command should be used?

Accepted Answer

rollback 0. The 'rollback 0' command reverts the candidate configuration to the last committed configuration, discarding all uncommitted changes. In Junos, the rollback command uses a numeric index where 0 always refers to the most recently committed configuration, effectively undoing any uncommitted edits.

Answer

delete configuration

Answer

clear configuration

Answer

load override terminal

Question 12

Refer to the exhibit. An administrator notices the /var partition is nearly full. Which command can be used to safely reclaim disk space?

Accepted Answer

request system storage cleanup. The 'request system storage cleanup' command safely removes old log files, core dumps, and other temporary files that are no longer needed, freeing up space on the /var partition without risking system stability. This is the recommended Junos method for reclaiming disk space because it targets only files that can be safely deleted.

Answer

request system reboot

Answer

delete /var/log/messages

Answer

request system software delete

Question 13

A static route is configured with next-hop 10.0.0.1, but the route does not appear in the routing table. The interface ge-0/0/0 has IP 192.168.1.2/24 and is up. What is the most likely reason?

Accepted Answer

The next-hop IP is not on a directly connected subnet.. D is correct because Junos requires the next-hop IP of a static route to be reachable via a directly connected subnet for the route to be installed in the routing table. Since the next-hop 10.0.0.1 is not on the same subnet as the interface ge-0/0/0 (192.168.1.2/24), the route remains hidden and does not appear in the routing table.

Answer

The static route has a preference of 5.

Answer

The route is hidden due to an import policy.

Answer

The static route is configured with the 'discard' option.

Question 14

Which TWO commands can be used to monitor system log messages in real-time?

Accepted Answer

monitor start messages. The 'monitor start messages' command streams the contents of the /var/log/messages file in real-time, allowing you to monitor system log messages as they are generated. 'monitor start interactive-commands' (Option D) monitors logs specific to interactive CLI commands, not general system log messages, so it does not satisfy the stem. The other options ('show log messages | last 100', 'show system log messages', 'show configuration system syslog') either display historical data or configuration, not real-time system log monitoring.

Answer

show log messages | last 100

Answer

show system log messages

Answer

show configuration system syslog

Answer

monitor start interactive-commands

Question 15

Refer to the exhibit. An administrator wants to see authentication-related logs like SSH logins. In the current configuration, which log file contains this information?

Accepted Answer

messages. In Junos, authentication-related logs such as SSH login attempts are recorded by default in the 'messages' log file. This file captures syslog messages for various system events, including authentication successes and failures. The 'interactive-commands' log file only logs user-executed CLI commands after successful login, not the authentication process itself. The 'security' log is intended for firewall and security policy events, and 'utmp' is for user accounting. Therefore, option D is correct.

Answer

utmp

Answer

interactive-commands

Answer

security