JN0-106 Practice Test 3 — 30 Questions

Question 1

Refer to the exhibit. A host connected to ge-0/0/1 cannot reach a host connected to ge-0/0/2 even though both are in VLAN10. What is the most likely cause?

Accepted Answer

The hosts are configured with IP addresses on different subnets.. Although both hosts are in the same VLAN and can communicate at Layer 2 (MAC addresses), IP communication requires them to be on the same IP subnet. If the hosts have IP addresses on different subnets, they will attempt to use a default gateway for routing. Without a router or IRB interface configured, the traffic cannot be delivered, leading to unreachability.

Answer

VLAN10 is not defined in the global VLAN configuration.

Answer

An IRB interface for VLAN10 is not configured.

Answer

The interface ge-0/0/2 is configured as a trunk port.

Question 2

A network engineer configures a static route to 10.0.0.0/8 with a preference of 20. An OSPF internal route to 10.0.0.0/8 has a default preference of 10. Which route will be active in the routing table?

Accepted Answer

The OSPF route, because of lower preference.. In Junos, the active route in the routing table is determined by the lowest preference value. OSPF internal routes have a default preference of 10, while static routes have a default preference of 5, but here the static route is configured with a preference of 20. Since OSPF's preference (10) is lower than the static route's preference (20), the OSPF route is chosen as active.

Answer

Both routes, because they have different protocols.

Answer

Neither, because of a conflict.

Answer

The static route, because it is manually configured.

Question 3

An engineer needs to apply a configuration change that adds a new static route to the Junos device. The engineer wants to ensure the change takes effect immediately and is persistent across reboots. Which command should the engineer use?

Accepted Answer

commit. The 'commit' command is correct because it immediately activates the candidate configuration (including the new static route) and makes it the active configuration that survives a reboot. Junos uses a two-stage configuration model where changes are first made to the candidate configuration and then committed to become the active, persistent configuration.

Answer

load override

Answer

commit confirmed

Answer

rollback

Question 4

A network administrator needs to temporarily disable a set of configuration statements for testing without deleting them. Which approach should be used?

Accepted Answer

use the 'deactivate' command to mark the statements inactive. The 'deactivate' command in Junos allows an administrator to temporarily disable a set of configuration statements without removing them from the configuration. When a statement is deactivated, it is prefixed with 'inactive:' in the configuration hierarchy, and the commit operation ignores it. This is ideal for testing changes, as the statements can be easily re-enabled using the 'activate' command.

Answer

delete the statements and later re-add from a backup

Answer

comment out the lines using #

Answer

set the configuration to a different group and remove apply-groups

Question 5

A network engineer is designing a redundant network with two Juniper routers running VRRP. The virtual IP address is 10.0.0.1. Both routers are configured as VRRP group 1. What is the purpose of the 'priority' parameter in VRRP configuration?

Accepted Answer

It determines the master router election.. In VRRP, the 'priority' parameter (range 1-254, default 100) is used to elect the master router. The router with the highest priority becomes the master for the virtual IP address 10.0.0.1, ensuring redundancy by taking over traffic forwarding if the current master fails.

Answer

It sets the interval for VRRP advertisements.

Answer

It determines the virtual MAC address.

Answer

It changes the virtual IP address.

Question 6

An engineer notices that a Juniper device is not saving configuration changes across reboots. What is the most likely cause?

Accepted Answer

The candidate configuration was not committed.. In Junos OS, configuration changes are stored in a candidate configuration and only become active and persistent across reboots after a 'commit' operation. Without a commit, the changes remain in the candidate buffer and are discarded upon reboot, causing the device to revert to the last committed configuration.

Answer

The rescue configuration is not set.

Answer

The device is booting from factory-default configuration.

Answer

The command 'request system reboot' was used instead of 'commit'.

Question 7

An engineer wants to apply a candidate configuration and automatically revert to the previous configuration after 10 minutes if the commit is not confirmed. Which command should be used?

Accepted Answer

commit confirmed 10. The `commit confirmed 10` command commits the candidate configuration and starts a 10-minute timer. If the commit is not explicitly confirmed with another `commit` command within that time, Junos automatically reverts to the previous configuration. This is the correct method for a timed automatic rollback after a commit.

Answer

commit at 10

Answer

set system commit timer 10

Answer

commit check

Question 8

A network engineer configures a static route to a remote network. They want the route to be automatically removed from the routing table if the directly connected interface used to reach the next hop fails. Which configuration approach should be used?

Accepted Answer

Configure the next-hop as the interface name.. Configuring the next-hop as an interface name (e.g., ge-0/0/0) creates a static route that is automatically removed from the routing table when that interface goes down. This is due to the route being 'qualified' by the interface's operational state; if the interface fails, the route is withdrawn. In contrast, using an IP address as the next-hop does not tie the route to the interface's state, so the route remains even if the interface fails, as long as the next-hop is reachable via another path.

Answer

Configure a higher metric on the static route.

Answer

Configure a preference of 0 on the static route.

Answer

Configure the next-hop as an IP address.

Question 9

Which command is used to verify that the current active configuration is the same as the candidate configuration?

Accepted Answer

show | compare. The command `show | compare` displays the differences between the candidate configuration and the active (committed) configuration. If there are no differences, the candidate configuration is identical to the active configuration. This is the correct way to verify whether the candidate configuration matches the active configuration in Junos.

Answer

commit check

Answer

show configuration

Answer

show system configuration

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

An engineer issues the 'rollback 3' command in configuration mode. What is the effect?

Accepted Answer

The candidate configuration is replaced with the configuration from three commits ago.. The 'rollback 3' command in Junos configuration mode replaces the current candidate configuration with the configuration from the third most recent commit. Junos maintains up to 50 rollback slots (numbered 0 through 49), where slot 0 is the most recent commit, slot 1 is the commit before that, and so on. Therefore, 'rollback 3' retrieves the configuration saved three commits ago, overwriting any uncommitted changes in the candidate configuration.

Answer

The candidate configuration is saved as the third rollback slot.

Answer

The active configuration is replaced with the candidate configuration.

Answer

The device reboots and loads configuration version 3.

Question 12

During troubleshooting, an engineer notices that BGP sessions are flapping. They suspect that the issue might be related to the maximum number of routes allowed. To see if the BGP import policy is rejecting routes, which operational command would provide immediate insight?

Accepted Answer

show bgp neighbor x.x.x.x. The 'show bgp neighbor x.x.x.x' command displays detailed BGP session information, including the number of received and accepted routes, as well as any prefix-limit or policy-related rejections. If the BGP import policy is rejecting routes due to exceeding the maximum allowed, this command will show the 'received prefixes' count alongside the 'accepted prefixes' count, immediately revealing if routes are being dropped. This provides direct insight into whether the flapping is caused by route limit enforcement.

Answer

show version

Answer

show interfaces terse

Answer

show route protocol bgp

Question 13

Which two commands display the IPv4 unicast routing table? (Choose two.)

Accepted Answer

show route. Option C, `show route`, is correct because on Junos devices this command displays the complete routing table, which by default is the IPv4 unicast table (inet.0), listing all learned and direct routes. Option D, `show route table inet.0`, is also correct because inet.0 is the specific routing table name for IPv4 unicast routes, so this command explicitly displays exactly that table. Option A, `show ip route`, is not a valid Junos command (it is Cisco IOS syntax), so it does not belong. Option B, `show route protocol ospf`, only filters and displays OSPF-learned routes rather than the entire IPv4 unicast routing table. Option E, `show routing`, is not a valid command and therefore cannot display the routing table.

Answer

show ip route

Answer

show route protocol ospf

Answer

show routing

Question 14

Which THREE statements correctly describe the behavior of the 'replace pattern' command in Junos configuration mode?

Accepted Answer

It can be used to change interface names or IP addresses throughout the configuration.. Option C is correct because the 'replace pattern' command performs a global find-and-replace across the candidate configuration, making it ideal for renaming interfaces or changing IP addresses everywhere they appear. Option D is correct because 'replace pattern' edits the candidate configuration, not the active configuration, so changes must still be committed to take effect. Option E is correct because the command matches text using regular expressions (e.g., 'replace pattern ge-0/0/0 with ge-0/0/1'), allowing flexible pattern-based substitutions. Option A is not correct because 'replace pattern' does not itself validate the replacement for correctness before applying; validation occurs at commit time via 'commit check' or the commit process. Option B is not correct because 'replace pattern' does not automatically commit changes; the user must explicitly issue a 'commit' command afterward.

Answer

It validates the replacement configuration for correctness before applying.

Answer

It automatically commits the changes after replacement.

Question 15

Which two commands can be used to display real-time interface information? (Choose two.)

Accepted Answer

monitor interface. Option A, `monitor interface`, is correct because it provides a real-time, continuously updating view of interface statistics such as traffic counters, errors, and link state on Juniper devices. Option B, `monitor traffic`, is correct because it captures and displays live packet-level traffic on an interface, showing real-time data as packets traverse the interface. Option C, `show log`, is incorrect because it displays stored log file contents rather than live interface information. Option D, `request system reboot`, is incorrect because it reboots the device and does not display interface data. Option E, `show system storage`, is incorrect because it reports disk and filesystem usage, not real-time interface information.

Answer

show log

Answer

request system reboot

Answer

show system storage

Question 16

Which THREE actions can be performed in operational mode on a Junos device?

Accepted Answer

Ping a remote host. In Junos, operational mode is the CLI mode entered after login (prompt user@host>), used for monitoring and controlling device state. Option B (Ping a remote host) is correct because the ping command is an operational-mode command used to test reachability to a remote host. Option D (View system logs) is correct because operational mode provides commands such as show log messages to inspect system log files. Option E (Reboot the chassis) is correct because the request system reboot command is executed from operational mode to restart the device. Options A and C are not operational-mode actions: committing configuration changes (commit) and configuring interface IP addresses (set interfaces ...) are performed in configuration mode, which is entered with the configure command.

Answer

Commit configuration changes

Answer

Configure interface IP addresses

Question 17

Which TWO statements about the rescue configuration are correct? (Choose two.)

Accepted Answer

The rescue configuration is designed to provide a method of last-resort recovery.. Option C is correct because the rescue configuration exists specifically as a last-resort recovery mechanism, allowing an administrator to return a device to a known-good configuration when the active configuration is broken or inaccessible. Option D is correct because on Junos devices the rescue configuration is created and stored by running the operational-mode command 'request system configuration rescue save', which snapshots the current candidate configuration as the rescue configuration. Option A is wrong because the rescue configuration is not saved automatically on every commit; it must be saved explicitly by the administrator. Option B is wrong because 'rollback rescue' loads the previously saved rescue configuration, not the factory-default configuration, which would be loaded with 'load factory-default' or 'rollback 0' depending on context. Option E is wrong because the rescue configuration restores the entire saved configuration, not just a subset of it.

Answer

The rescue configuration is automatically saved after every commit.

Answer

The 'rollback rescue' command loads the factory-default configuration.

Answer

The rescue configuration can be used to restore only a subset of the configuration.

Question 18

An engineer needs to check the last time the configuration was changed. Which command provides this information?

Accepted Answer

show system commit. The 'show system commit' command displays the commit history, including the date, time, and user for each configuration change. This allows the engineer to see exactly when the last configuration was committed, which is the definitive way to determine the last time the configuration was changed.

Answer

show configuration | display set

Answer

show system alarms

Answer

show system uptime

Question 19

While in configuration mode, an engineer types 'show' and sees a different output than when typing 'run show configuration'. Why?

Accepted Answer

'show' shows the candidate configuration; 'run show configuration' shows the active configuration.. In Junos, when you are in configuration mode and type 'show', it displays the candidate configuration (the changes you have made but not yet committed). The command 'run show configuration' executes the operational-mode command 'show configuration' from within configuration mode, which displays the active (committed) configuration. Therefore, option B correctly identifies that 'show' shows the candidate configuration and 'run show configuration' shows the active configuration.

Answer

'show' shows the active configuration; 'run show configuration' shows the candidate.

Answer

Both commands produce identical output.

Answer

'run show configuration' is not allowed from configuration mode.

Question 20

Which THREE of the following are characteristics of configuration groups in Junos?

Accepted Answer

The 'apply-groups' statement is used to specify which group(s) should be inherited.. Option A is correct because Junos uses the 'apply-groups' statement (and 'apply-groups-except') to specify which configuration group(s) a given hierarchy level should inherit from. Option C is correct because Junos configuration groups support nesting: a group can itself contain an 'apply-groups' statement, allowing one group to inherit from another group. Option D is correct because the core purpose of configuration groups is to define a reusable set of configuration statements once and have them inherited by multiple sections of the configuration, reducing duplication. Option B is incorrect because there is no limit of 10 groups per statement; Junos allows up to 50 groups to be applied at a single hierarchy level. Option E is incorrect because statements inherited from a group can be overridden by explicitly configuring the same statement in the main configuration, which takes precedence over the inherited value.

Answer

A maximum of 10 groups can be applied to a single configuration statement.

Answer

Configuration groups do not allow individual statements within the group to be overridden in the main configuration.