JN0-106 Practice Test 12 — 15 Questions

Question 1

A network engineer needs to restore the factory-default configuration on a Junos device. Which command sequence is correct?

Accepted Answer

load factory-default and then commit. The correct command sequence to restore factory-default configuration on a Junos device is 'load factory-default' followed by 'commit'. The 'load factory-default' command replaces the current candidate configuration with the factory-default configuration, but it does not take effect until a 'commit' is issued. This ensures the device reverts to its original settings without affecting the currently running configuration until explicitly committed.

Answer

set system host-name factory-default

Answer

request system zeroize

Answer

delete configuration and reboot

Question 2

Which TWO statements describe correct methods to enter configuration mode? (Choose two.)

Accepted Answer

Type 'edit' at the operational mode prompt.. The 'edit' command transitions from operational mode into configuration mode. Option B is correct because the 'configure exclusive' command enters configuration mode in exclusive mode, which is a valid method. Option C is correct because the 'configure' command enters configuration mode in shared mode. Options D and E are invalid commands in Junos OS.

Answer

Type 'cli' at the operational mode prompt.

Answer

Type 'expert' at the operational mode prompt.

Question 3

A network engineer needs to upgrade Junos on an MX router with dual Routing Engines (RE0 and RE1). What is the recommended procedure to minimize downtime?

Accepted Answer

Upgrade the backup RE, perform a graceful switchover (RESTART ROUTING), then upgrade the former primary. It minimizes downtime by first upgrading the backup RE (RE1), then performing a graceful Routing Engine switchover (using the 'request chassis routing-engine master switch' command or equivalent), which causes the upgraded backup to become the new primary without disrupting traffic. After the switchover, the former primary (now the backup) can be upgraded and rebooted, ensuring that at least one RE is always processing traffic and routing protocols like BGP and OSPF maintain their adjacencies.

Answer

Upgrade the primary RE first, then the backup

Answer

Reboot both REs at the same time after copying the image

Answer

Upgrade both REs simultaneously using the same image

Question 4

Which two factors determine whether a route is active for a given destination when multiple routes from different protocols exist? (Choose two.)

Accepted Answer

Route preference. B is correct because Junos uses route preference (administrative distance) as the primary tiebreaker when multiple routing protocols offer routes to the same destination. The route with the lowest preference value is installed into the routing table as the active route. D is correct because even if a route has the best preference, it must have a reachable next hop to be considered active; if the next hop is unreachable, the route is hidden and not used.

Answer

Metric

Answer

Route origin

Answer

Local preference

Question 5

Refer to the exhibit. The network administrator made a change that caused connectivity loss. They need to revert to the configuration before the most recent commit. Which command would accomplish this?

Accepted Answer

rollback 1. In Junos, rollback numbers are stored with 0 being the most recent committed configuration. To revert to the configuration before the most recent commit, you need to load the configuration that was active before that change. That is rollback 1, which represents the second most recent commit. Using rollback 0 would load the configuration that caused the issue, not fix it.

Answer

rollback 0

Answer

rollback 3

Answer

rollback 2

Question 6

A network administrator is trying to configure a firewall filter on a Juniper device. They enter configuration mode and type 'set firewall family inet filter BLOCK-ICMP term 1 from protocol icmp'. They then type 'set firewall family inet filter BLOCK-ICMP term 1 then reject'. After committing, they notice that ICMP traffic is not being blocked. They run 'show configuration firewall' and see the filter is present. They run 'show firewall filter BLOCK-ICMP' to see the counters and notice the packet count is zero. What is the most likely reason?

Accepted Answer

The filter is not applied to any interface.. A firewall filter in Junos must be applied to an interface to take effect. Simply configuring the filter under the 'edit firewall' hierarchy does not activate it; the filter must be referenced with a 'family inet' statement under the interface configuration (e.g., 'set interfaces ge-0/0/0 unit 0 family inet filter input BLOCK-ICMP'). Without this application, the filter exists in the configuration but never processes traffic, resulting in zero packet counts.

Answer

The protocol icmp is not correct; it should be 'icmp6'.

Answer

The term 'then reject' should be 'then discard'.

Answer

The filter must be applied under the 'edit firewall' hierarchy.

Question 7

A junior engineer is troubleshooting connectivity issues and wants to trace the path packets take to a remote destination. Which Junos command should be used?

Accepted Answer

traceroute. The 'traceroute' command in Junos is specifically designed to trace the path packets take to a remote destination by sending UDP probes with increasing TTL values and analyzing ICMP Time Exceeded messages from intermediate routers. This directly addresses the junior engineer's need to map the Layer 3 path and identify where connectivity failures occur.

Answer

monitor traffic

Answer

show route

Answer

ping

Question 8

A junior administrator wants to view the current active configuration on a Juniper device. Which operational mode command should be used?

Accepted Answer

show configuration. The 'show configuration' command displays the current active configuration in the candidate configuration format, which is the configuration that is currently committed and running on the Juniper device. Option D is correct because it directly retrieves the active configuration from the /config/juniper.conf file, which is the authoritative source for the operational configuration.

Answer

show configuration | display set

Answer

show system services

Answer

show interfaces terse

Question 9

A company has a Juniper MX router acting as a BGP route reflector. The router has two routing instances: 'internet' and 'management'. The 'internet' instance uses a firewall filter to block traffic to the router's loopback address from external sources. After a recent configuration change, the engineer notices that SSH access to the router's loopback IP (10.0.0.1) from the internal management network (192.168.0.0/16) is being dropped. The firewall filter for the loopback interface in the 'internet' instance is correctly configured to allow traffic from 192.168.0.0/16. The management instance has no firewall filter applied. The engineer suspects that the issue is related to how the routing instances interact with the loopback interface. Which of the following is the most likely cause and solution?

Accepted Answer

The firewall filter applied to the loopback interface is shared across all routing instances; use a separate interface for management traffic or apply the filter only to the 'internet' instance's logical system.. In Junos, firewall filters applied to the loopback interface (lo0) are shared across all routing instances by default because the loopback is a single physical interface. Even though the filter is configured in the 'internet' instance, it affects traffic destined to the loopback IP from any instance, including the 'management' instance. To isolate management traffic, you must either use a separate physical interface or apply the filter only to the 'internet' instance's logical system (e.g., using a firewall filter with a routing-instance match condition).

Answer

The management instance needs a firewall filter that allows SSH; add a filter to the management instance's loopback.

Answer

The firewall filter in the 'internet' instance incorrectly blocks SSH; modify the filter to allow SSH from any source.

Answer

The BGP configuration is causing the loopback to be unreachable; disable BGP on the management instance.

Question 10

A technician needs to load a new configuration file that replaces only the specific hierarchy paths present in the file, leaving all other existing configuration unchanged. Which load statement is appropriate?

Accepted Answer

load merge. The 'load merge' command is correct because it merges the contents of the specified configuration file with the current candidate configuration, adding or updating only the hierarchy paths present in the file while preserving all other existing configuration. This matches the requirement to replace only specific hierarchy paths without affecting the rest of the configuration.

Answer

load replace

Answer

load set

Answer

load override

Question 11

A network engineer wants to quickly restore the device to a known good configuration after a failed change. What is the recommended approach?

Accepted Answer

Use the 'rollback rescue' command.. The 'rollback rescue' command restores the device to the rescue configuration, which is a known good configuration saved explicitly for recovery after a failed change. The rescue configuration is stored as a separate file and is not affected by normal commit operations, making it the recommended approach for quick restoration.

Answer

Use the 'request system configuration rescue save' command.

Answer

Use the 'rollback 0' command.

Answer

Use the 'load override terminal' command.

Question 12

Refer to the exhibit. What is the purpose of the 'unit 0' statement?

Accepted Answer

Defines a logical interface.. In Junos, the 'unit 0' statement is used to define a logical interface (also known as a subinterface) under a physical interface. Every physical interface must have at least one logical unit, and unit 0 is the default logical interface that carries Layer 3 configuration such as IP addresses. This is fundamental to Junos architecture, where all protocol configurations are applied at the logical unit level, not the physical interface level.

Answer

Enables IPv6.

Answer

Sets the MTU.

Answer

Defines a physical interface.

Question 13

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

Accepted Answer

The next-hop address is not reachable in the routing table.. For a static route to be active in the JUNOS routing table, the next-hop address must be reachable via an active route in the routing table. If the next-hop is not reachable, the static route is considered invalid and will not be installed as active, even if the outbound interface is up and the configuration is committed.

Answer

The static route has a high preference.

Answer

The outbound interface is not up.

Answer

The static route is not committed.

Question 14

A company has multiple Juniper devices and wants to standardize configuration snapshots for backup and audit purposes. What is the best practice?

Accepted Answer

Use 'show configuration | save /var/tmp/config.txt' and then transfer the file via SCP to a backup server. It uses the 'show configuration | save' command to write the current active configuration to a file in /var/tmp, which can then be securely transferred via SCP to a backup server. This is the standard Junos method for creating a portable, text-based snapshot of the configuration for backup and audit purposes, as it preserves the exact configuration syntax and can be easily compared or restored.

Answer

Run 'commit and-quit' to save the configuration to the flash

Answer

Use the 'file archive' command to create a backup of the configuration

Answer

Use the 'show configuration | no-more' command and copy the output manually

Question 15

You are troubleshooting a network connectivity issue at a medium-sized company that uses Juniper EX4300 switches. Users in VLAN 100 (10.10.100.0/24) report that they cannot access a server in VLAN 200 (10.10.200.0/24). The switch has IRB interfaces configured for both VLANs and is acting as the default gateway. The IRB interfaces are up and have correct IP addresses. The server and users have correct IP configurations. 'show arp' on the switch shows incomplete entries for some hosts in VLAN 100. 'show ethernet-switching table' shows MAC addresses for users are present on the correct access ports. However, pings from the switch to a user in VLAN 100 fail. What is the most likely issue?

Accepted Answer

The switch cannot resolve ARP requests because the user's host is not responding.. The 'incomplete' entries in the 'show arp' output indicate that the switch sent ARP requests for hosts in VLAN 100 but received no replies. Since the switch is the default gateway, it must resolve the Layer 2 MAC address of each host to forward traffic. If a user's host is not responding to ARP (e.g., due to a firewall, misconfiguration, or the host being offline), the switch cannot complete the ARP cache entry, causing pings from the switch to fail and potentially disrupting inter-VLAN routing.

Answer

Spanning Tree Protocol is blocking the user ports.

Answer

A static MAC address entry for the server is missing.

Answer

The IRB interface for VLAN 100 is not configured with a proxy ARP.