JNCIA-JUNOS Practice Test 2 — 25 Questions

Question 1

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. Option D is correct because 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 2

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 3

Which TWO statements are true about the Junos OS candidate configuration model? (Choose two.)

Accepted Answer

The candidate configuration can be modified without affecting the active configuration.. Option D is correct because the Junos OS candidate configuration model allows modifications to be made to a separate candidate configuration file without affecting the active configuration currently running on the device. This ensures that changes can be staged, reviewed, and validated before being committed, providing a safe and non-disruptive way to manage configuration changes.

Answer

Each change is applied incrementally to the active configuration.

Answer

The candidate configuration is stored in a separate file from the active configuration.

Answer

After a commit, the candidate configuration is automatically discarded.

Question 4

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 5

A network administrator notices that traffic between two VLANs is not reaching its destination. The switch has an IRB interface configured with an IP address in each VLAN's subnet. What is the most likely missing configuration?

Accepted Answer

The VLANs are not defined on the switch.. The IRB interface provides Layer 3 routing between VLANs, but it requires the VLANs themselves to be defined on the switch. If the VLANs are not defined, the switch cannot associate the IRB interface with the correct broadcast domains, and traffic will not be forwarded between them. Option C correctly identifies this missing configuration.

Answer

The IRB interface does not have an IP address configured.

Answer

The VLANs are on different switches.

Answer

The switch ports are not configured for VLAN tagging.

Question 6

Which TWO statements about Juniper's implementation of static routes are correct? (Choose two.)

Accepted Answer

The default preference for static routes is 5.. Option A is correct because in Juniper's Junos OS, the default preference (administrative distance) for static routes is 5. This value indicates that static routes are highly trusted, only surpassed by directly connected routes (preference 0). This is a Juniper-specific default, differing from Cisco's default of 1 for static routes.

Answer

Static routes always have a metric of 1.

Answer

Static routes are automatically redistributed into OSPF.

Answer

The default preference for static routes is 170.

Question 7

A network engineer is troubleshooting OSPF adjacencies between two Juniper routers. The routers are directly connected and have matching OSPF configurations except for the router IDs. Router A has router-id 10.0.0.1, Router B has router-id 10.0.0.2. The adjacency remains in the EXSTART state. What is the most likely cause?

Accepted Answer

The MTU on the interface is mismatched.. The EXSTART state indicates that the routers have progressed past the 2-Way state and are attempting to exchange Database Description (DBD) packets. A common cause for getting stuck in EXSTART is an MTU mismatch, because OSPF uses the interface MTU to determine the maximum size of DBD packets. If Router A's MTU is larger than Router B's, Router B will drop the oversized DBD packet and the adjacency will remain in EXSTART.

Answer

The router IDs are not the same.

Answer

The area ID is not configured.

Answer

The hello and dead intervals are mismatched.

Question 8

Which THREE of the following statements are true regarding Junos OS commit operations?

Accepted Answer

The 'commit check' command validates the candidate configuration without activating it.. Option A is correct because the 'commit check' command validates the candidate configuration for syntax and semantic errors without activating it. This allows an administrator to verify changes before making them active, preventing potential misconfigurations from disrupting network operations.

Answer

You can run multiple commit scripts during a single commit operation.

Answer

The rollback command reverts to the current active configuration.

Question 9

Which THREE commands are valid Junos operational mode commands for monitoring network diagnostics? (Choose three.)

Accepted Answer

traceroute. Option A is correct because the 'traceroute' command in Junos operational mode sends a series of UDP packets with increasing TTL values to discover the path a packet takes to a destination, which is a standard network diagnostic tool. It is a valid operational mode command used for monitoring network connectivity and path analysis.

Answer

show configuration

Answer

request system reboot

Question 10

A network engineer needs to commit a configuration change but wants to ensure the change can be easily reverted if it causes issues. Which approach should the engineer take?

Accepted Answer

Use the 'commit confirmed' command with a timeout.. Option B is correct because the 'commit confirmed' command allows the engineer to commit a configuration change with a default timeout of 10 minutes (configurable). If the change causes issues and the engineer does not confirm the commit within the timeout period, Junos automatically reverts to the previous active configuration, providing a safe rollback mechanism.

Answer

Use the 'commit and-quit' command to apply changes.

Answer

Use the 'commit check' command before committing.

Answer

Use the 'rollback 0' command after committing.

Question 11

During troubleshooting, an engineer needs to view real-time logging messages on a Junos device. Which command should be used?

Accepted Answer

monitor start messages. The 'monitor start messages' command enables real-time, tail-like display of the /var/log/messages log file on a Junos device, allowing the engineer to view new log entries as they are generated. This is the correct command for live troubleshooting because it continuously updates the terminal with incoming syslog messages, unlike static file viewing commands.

Answer

file show /var/log/messages

Answer

show log messages

Answer

traceoptions

Question 12

An administrator wants to view the current operational status of interface ge-0/0/1 on a Junos device. Which command displays this information?

Accepted Answer

show interfaces terse ge-0/0/1. The 'show interfaces terse ge-0/0/1' command displays a concise, one-line summary of the operational status of the specified interface, including its administrative and link state, protocol status, and configured IP addresses. This is the correct command for viewing the current operational status because 'terse' filters the output to show only the essential operational details without configuration data.

Answer

show configuration interfaces ge-0/0/1

Answer

monitor interface ge-0/0/1

Answer

show interface ge-0/0/1

Question 13

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 14

A junior engineer is troubleshooting a routing issue and wants to see the route table for IPv4 unicast routes. Which command will display this information?

Accepted Answer

show route table inet.0. Option A is correct because the command 'show route table inet.0' displays the IPv4 unicast route table in Junos. The inet.0 table is the default routing table for IPv4 unicast routes, containing all active routes learned via various protocols (e.g., OSPF, BGP, static). This command is the standard way to view the IPv4 unicast routing information base (RIB) on Juniper devices.

Answer

show route table inet6.0

Answer

show route forwarding-table

Answer

show route protocol bgp

Question 15

An administrator wants to see the differences between the candidate configuration and the active configuration. Which command should be used?

Accepted Answer

show | compare. The 'show | compare' command displays the differences between the candidate configuration and the active (committed) configuration. This is the standard Junos method for reviewing uncommitted changes before committing them, as it outputs a diff-style output showing lines added, deleted, or modified.

Answer

show | display set

Answer

run show configuration

Answer

show configuration

Question 16

Refer to the exhibit. An engineer runs the command but sees no output. What is the most likely reason?

Accepted Answer

The interface ge-0/0/0 is not configured.. The command 'show configuration | display set' outputs the configuration in a set-based format. If there is no output, it means the configuration is empty or the specified interface does not exist. In this case, the interface ge-0/0/0 is not configured, so the filter 'display set' returns no lines for that interface. Option B is correct because an unconfigured interface yields no configuration output.

Answer

The pipe (|) is not supported with 'display set'.

Answer

The interface name is misspelled.

Answer

The command syntax is incorrect.

Question 17

Which TWO statements are true regarding the Junos CLI? (Choose two.)

Accepted Answer

The pipe (|) can be used to filter command output.. Option A is correct because the pipe (|) in the Junos CLI is used to filter command output, allowing you to apply modifiers like 'match', 'except', 'count', or 'display set' to refine the displayed information. This is a fundamental feature for efficiently managing large amounts of operational or configuration data.

Answer

The 'edit' command is used in operational mode to navigate the hierarchy.

Answer

The 'set' command is used in operational mode to set parameters.

Answer

The 'rollback 0' command discards the candidate configuration.

Question 18

Which THREE are valid methods to exit configuration mode in Junos? (Choose three.)

Accepted Answer

exit configuration-mode. Option A is correct because 'exit configuration-mode' is a valid operational mode command that explicitly exits from configuration mode back to operational mode. This command is used when you are at the top of the configuration hierarchy and want to leave the configuration CLI session.

Answer

commit check

Answer

quit

Question 19

A network engineer is configuring a new Juniper device. They intend to apply a firewall filter to an interface to only allow SSH traffic from a specific management subnet. Which configuration approach best follows Juniper best practices?

Accepted Answer

Define the filter under 'firewall family inet' and apply it under 'interfaces ge-0/0/0 unit 0 family inet filter input filter-name'. Option A is correct because it follows Juniper best practices by defining the firewall filter under the `firewall family inet` hierarchy (which is the standard location for IPv4 filters) and applying it as an input filter on the physical interface `ge-0/0/0 unit 0 family inet`. This configuration ensures that only SSH traffic from the specified management subnet is permitted inbound on that interface, while all other traffic is dropped by default (since firewall filters in Junos have an implicit deny at the end).

Answer

Define the filter under 'firewall family inet' and apply it under 'interfaces lo0 unit 0 family inet filter input filter-name'

Answer

Define the filter under 'firewall family inet' and apply it under 'interfaces ge-0/0/0 unit 0 family inet input'

Answer

Define the filter under 'firewall family any' and apply it under 'interfaces ge-0/0/0 unit 0 family any filter input'

Question 20

An engineer is designing a network and needs to ensure that management traffic (SSH, SNMP) is always permitted, even if an interface firewall filter is applied. Which Juniper best practice should be followed?

Accepted Answer

Apply a firewall filter on the loopback interface (lo0) to protect the device. Applying a firewall filter to the loopback interface (lo0) is the Juniper best practice for protecting management traffic because the loopback interface is the logical termination point for all control plane traffic, including SSH and SNMP. This ensures that management traffic is always permitted regardless of which physical interface it arrives on, while still allowing interface-specific filters to be applied for data plane traffic without risk of blocking management access.

Answer

Use a firewall filter that permits all management traffic at the top of the list on each interface

Answer

Apply a firewall filter to the management interface (fxp0)

Answer

Disable the firewall filter on all interfaces