JN0-106 Practice Questions 1 — 50 Questions

Question 1

When configuring a new Juniper router, an engineer needs to ensure that configuration changes are not automatically committed after a certain time if not explicitly confirmed. Which configuration parameter controls this?

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

Accepted Answer

commit confirmed. The 'commit confirmed' command is used to apply a configuration change that will automatically roll back to the previous configuration if not explicitly confirmed within a specified time period (default 10 minutes). This ensures that changes are not permanently applied unless the engineer verifies them, preventing accidental lockout or misconfiguration.

Answer

commit check

Answer

commit at

Answer

commit synchronize

Question 2

Which THREE route types are considered protocol-independent in Junos?

Accepted Answer

Direct routes. Direct, local, and static routes are considered protocol-independent because they are not learned or installed by any dynamic routing protocol. Direct routes are automatically created for directly connected interfaces, local routes represent the interface's own IP address, and static routes are manually configured by an administrator. These routes exist in the routing table regardless of whether any routing protocol is running, hence the term 'protocol-independent'.

Answer

BGP routes

Answer

OSPF routes

Question 3

You are troubleshooting an OSPF issue on a Juniper router. The router has a single interface ge-0/0/1 with IP 10.1.1.1/30 connected to a neighbor with IP 10.1.1.2/30. OSPF is configured area 0. The 'show ospf neighbor' command shows no neighbors. 'show interfaces ge-0/0/1 terse' shows the interface is up. 'show configuration protocols ospf' shows:
   area 0.0.0.0 {
       interface ge-0/0/1.0 {
           passive;
       }
   }
What is the problem?

Accepted Answer

The OSPF interface is configured as passive. The 'passive' statement under the OSPF interface configuration prevents the router from sending or processing OSPF Hello packets on that interface. Without Hello packets, the router cannot discover neighbors or form adjacencies, which is why 'show ospf neighbor' returns no neighbors even though the interface is operationally up.

Answer

The hello timer is too slow

Answer

Authentication is missing

Answer

The interface is administratively down

Question 4

A network engineer wants to schedule a reboot of a Juniper device at 3:00 AM. Which command should be used?

Accepted Answer

request system reboot at 03:00. The 'request system reboot at 03:00' command schedules a one-time reboot of the Juniper device at the specified time (3:00 AM). The 'at' parameter allows the engineer to set an absolute time for the reboot, which is the exact requirement for scheduling a reboot at a specific future time.

Answer

request system configuration rescue save

Answer

request system reboot

Answer

load override /config/juniper.conf.gz

Question 5

A junior engineer needs to collect a snapshot of the current system state, including routing tables, interfaces, and configuration, for a support ticket. Which command achieves this?

Accepted Answer

request support information. The 'request support information' command is the correct choice because it collects a comprehensive snapshot of the current system state, including routing tables, interface details, configuration, logs, and other operational data into a single archive file. This is specifically designed for support tickets, as it bundles all relevant diagnostic information in one step, unlike individual show commands that only capture partial data.

Answer

show configuration

Answer

show interfaces

Answer

show route

Question 6

A network engineer needs to revert to the configuration that was active before the last commit. Which command accomplishes this?

Accepted Answer

rollback 1. The 'rollback 1' command reverts the active configuration to the configuration that was committed immediately before the most recent commit. Junos maintains up to 50 previous committed configurations (rollback 0 being the current active configuration, rollback 1 the previous, and so on). This command is the correct way to undo the last commit without manually editing the configuration.

Answer

rollback 0

Answer

load override

Answer

revert

Question 7

During a maintenance window, an engineer needs to apply a series of configuration changes that are stored in a text file. Which command sequence should be used to load and apply the changes from the file?

Accepted Answer

configure; load merge /var/tmp/changes.txt; commit. The engineer needs to enter configuration mode (configure) and then use the 'load merge' command to merge the contents of the text file into the candidate configuration without replacing the entire configuration. The 'commit' command then activates the changes. This is the standard Junos workflow for applying incremental changes from a file.

Answer

request system configuration rescue save

Answer

load override /var/tmp/changes.txt; commit

Answer

configure; load patch /var/tmp/changes.txt; commit

Question 8

Which Junos command displays the route to a specific IP address, including the active route and any backup routes?

Accepted Answer

show route 192.168.1.1. The 'show route 192.168.1.1' command in Junos displays all routes in the routing table that match the specified destination, including the active route (marked with '>') and any backup routes (marked with a space). This command provides a comprehensive view of the forwarding table entries for that prefix, which is essential for understanding both primary and failover paths.

Answer

show route protocol

Answer

show route active

Answer

show route table

Question 9

A network engineer needs to make a change to a Junos device and ensure the change can be reverted if it causes issues. Which feature should be used?

Accepted Answer

commit confirmed. The `commit confirmed` command allows an engineer to commit a configuration change with a timer (default 10 minutes). If the change causes issues and the engineer does not confirm the commit within the timer, the device automatically reverts to the previous active configuration. This provides a safety net to revert changes without manual intervention.

Answer

configure exclusive

Answer

commit check

Answer

rollback 0

Question 10

Refer to the exhibit. An administrator notices repeated failed login attempts. What should be configured to mitigate this attack?

Accepted Answer

Configure a firewall filter to block the source IP. A firewall filter can block traffic from the source IP address of the repeated failed login attempts, preventing further access from that host. This is a direct and immediate mitigation against an ongoing brute-force attack, as it stops the attacker's traffic at the network layer before it reaches the SSH or login service.

Answer

Set login retry limit

Answer

Disable SSH

Answer

Change the root password

Question 11

Which command shows the operational status of all interfaces in a brief format?

Accepted Answer

show interfaces terse. The 'show interfaces terse' command displays a brief, one-line summary of each interface, including its administrative status (up/down), link status, protocol status, and configured IP addresses. This is the correct command for a concise overview of all interfaces' operational state, as specified in the Junos OS documentation.

Answer

show interfaces statistics

Answer

show interfaces detail

Answer

show configuration interfaces

Question 12

Refer to the exhibit. An engineer sees that the interface ge-0/0/0 has 'Admin up' and 'Link up'. What does this indicate?

Accepted Answer

The interface is up and the physical link is up.. When an interface shows 'Admin up' and 'Link up', it means the interface has been administratively enabled (no 'shutdown' command applied) and the physical layer has detected a carrier signal from the connected device. In Junos, this is the normal operational state for a functioning interface, confirming that both the administrative configuration and the physical link are active.

Answer

The interface is administratively down.

Answer

The interface is a loopback interface.

Answer

The interface has an IPv6 address only.

Question 13

A junior network administrator is setting up a Juniper MX router for the first time. After powering on the device, the administrator notices that the LED on the front panel blinks amber and the device does not complete the boot process. The console displays messages reporting file system errors. The administrator has no previous configuration changes and the device was shipped with factory defaults. Which action should the administrator take to resolve the boot issue?

Accepted Answer

Boot into single-user mode and run file system checks.. The amber blinking LED and file system errors indicate a corrupted file system, which is common on factory-default devices if the flash memory was not properly initialized. Booting into single-user mode (option A) allows the administrator to run 'fsck' (file system check) to repair the root file system without loading the full Junos OS, which is the standard recovery procedure for such boot failures.

Answer

Perform a password recovery procedure to gain access.

Answer

Use the 'request system software add' command from the boot loader.

Answer

Reinstall the Junos OS using a USB flash drive with the software image.

Question 14

A network engineer is configuring a new Juniper device and needs to ensure that the configuration is saved persistently across reboots. Which command should be used?

Accepted Answer

commit. The `commit` command activates the candidate configuration and saves it to the active configuration database, ensuring it persists across reboots. Without a commit, any changes made in candidate mode are lost when the device restarts.

Answer

save

Answer

request system reboot

Answer

show configuration

Question 15

A router is experiencing intermittent packet loss. The engineer runs 'show interfaces ge-0/0/0 extensive' and notices a high number of input errors but no output errors. What is the most likely cause?

Accepted Answer

A faulty transceiver. A high number of input errors with no output errors on a Juniper interface typically indicates a Layer 1 issue at the receiving end. A faulty transceiver can cause signal degradation, leading to CRC errors, framing errors, or alignment errors, all of which are counted as input errors. Since output errors are absent, the problem is not with the router's transmission but with the incoming signal quality.

Answer

The cable is too long

Answer

MTU mismatch

Answer

The interface is oversubscribed

Question 16

A user wants to discard all uncommitted changes and return to the last committed configuration without exiting configuration mode. Which command should they use?

Accepted Answer

rollback 0. 'rollback 0' discards all uncommitted changes and reverts the candidate configuration to the last committed configuration, all while staying in configuration mode. In Junos, rollback 0 specifically refers to the most recently committed configuration, making it the exact command to undo uncommitted edits without exiting.

Answer

load override

Answer

reload

Answer

commit check

Question 17

A network engineer is in configuration mode and wants to see the configuration in a format that can be directly pasted into another router to reproduce the configuration. Which output modifier should they use?

Accepted Answer

| display set. The '| display set' output modifier converts the current Junos configuration into a series of 'set' commands. This format is directly pasteable into another router's CLI to reproduce the exact configuration, making it ideal for configuration migration or backup restoration.

Answer

| display inheritance

Answer

| display xml

Answer

| count

Question 18

A junior engineer accidentally enters 'set interfaces ge-0/0/0 unit 0 family inet address 192.0.2.1/24' in operational mode. What will happen?

Accepted Answer

An error message is displayed, and no changes are made.. In Junos OS, the 'set' command is a configuration mode command used to modify the candidate configuration. When entered in operational mode (indicated by the '>' prompt), the CLI does not recognize it as a valid operational command. Junos will immediately display an error message such as 'unknown command' and make no changes to the running or candidate configuration.

Answer

The IP address is configured successfully.

Answer

The command is queued for later execution.

Answer

The CLI automatically switches to configuration mode.

Question 19

A network engineer notices that traffic to a critical server is being dropped intermittently. The server is reachable via a static route on the Juniper router. The engineer checks the routing table and sees the route is present. Which operational command should the engineer use next to isolate the issue?

Accepted Answer

show route forwarding-table destination 10.0.0.1. The `show route forwarding-table destination 10.0.0.1` command displays the actual forwarding entry in the kernel's forwarding table (FIB). Even if the route is present in the routing table (RIB), a mismatch between the RIB and FIB can cause traffic drops. This command directly verifies whether the route has been installed into the forwarding table, isolating the issue to a possible hardware or kernel programming failure.

Answer

show interfaces terse

Answer

show route 10.0.0.1

Answer

show arp

Question 20

Refer to the exhibit. An engineer notices that SNMP traffic from source 10.1.1.1 is being rejected on interface ge-0/0/1. The engineer wants to allow SNMP from this source while still blocking other SNMP traffic from the 10.0.0.0/8 range. Which change should be made?

Accepted Answer

Insert a term 0 before term 1 to permit SNMP from 10.1.1.1. Firewall filters in Junos are evaluated sequentially from the lowest term number. By inserting a new term 0 before the existing term 1 that explicitly permits SNMP traffic (UDP ports 161/162) from source 10.1.1.1, the filter will match and accept this traffic before reaching the deny term for the 10.0.0.0/8 range. This ensures the specific host is allowed while still blocking other SNMP traffic from the broader subnet.

Answer

Add a term at the end to permit all from 10.1.1.1

Answer

Change the source-address in term 1 to 10.0.0.0/8 except 10.1.1.1

Answer

Remove the filter and apply a new filter that permits SNMP from 10.1.1.1