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CCNA Junos User Interfaces Questions

75 of 97 questions · Page 1/2 · Junos User Interfaces topic · Answers revealed

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1
MCQmedium

You are managing a Juniper EX4300 switch that serves as a Layer 3 access switch for a campus network. The switch has multiple VLANs configured with IRB interfaces. Users in VLAN 10 report that they cannot reach the default gateway (IRB.10) even though other VLANs are working fine. You check the configuration and see that interface irb.10 is configured with an IP address. You also verify that the VLAN is associated with the correct access ports. However, when you ping the IRB.10 address from the switch itself, it fails. You suspect that the issue might be that the IRB interface is not 'up'. Which command would you use to quickly verify the operational status of the IRB interface?

A.show interfaces terse irb.10
B.show ethernet-switching table
C.show configuration interfaces irb.10
D.show vlan
AnswerA

Shows operational status of the IRB interface.

Why this answer

Option A is correct because `show interfaces terse irb.10` displays the operational status (up/down) of the IRB interface along with its configured IP address. Since the issue is that the IRB interface may not be 'up', this command quickly confirms whether the interface is operationally active, which is essential for Layer 3 forwarding.

Exam trap

The trap here is that candidates often check the configuration (`show configuration`) assuming it reflects the operational state, but Junos separates configuration from operational status, so a correctly configured IRB can still be down due to missing VLAN association or no active member ports.

How to eliminate wrong answers

Option B is wrong because `show ethernet-switching table` displays MAC address-to-VLAN mappings for Layer 2 forwarding, not the operational status of IRB interfaces. Option C is wrong because `show configuration interfaces irb.10` only shows the configured (intended) settings, not the current operational state; the interface could be configured but still down. Option D is wrong because `show vlan` displays VLAN membership and associated interfaces but does not show the operational status of IRB interfaces or their IP addresses.

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2
MCQmedium

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

A.'show' shows the active configuration; 'run show configuration' shows the candidate.
B.'show' shows the candidate configuration; 'run show configuration' shows the active configuration.
C.Both commands produce identical output.
D.'run show configuration' is not allowed from configuration mode.
AnswerB

Correct explanation of the difference.

Why this answer

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.

Exam trap

The trap here is that candidates often confuse the behavior of 'show' in configuration mode with the operational-mode 'show configuration' command, mistakenly thinking both display the same configuration or that 'show' always shows the active configuration.

How to eliminate wrong answers

Option A is wrong because it reverses the roles: 'show' shows the candidate configuration, not the active configuration, and 'run show configuration' shows the active configuration, not the candidate. Option C is wrong because the two commands produce different outputs: 'show' displays the candidate configuration (which may include uncommitted changes), while 'run show configuration' displays the active (committed) configuration. Option D is wrong because 'run show configuration' is allowed from configuration mode; the 'run' command is specifically designed to execute operational-mode commands while in configuration mode.

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3
MCQmedium

A network engineer is configuring a Juniper device in a production network. They have applied several changes to the candidate configuration and run 'commit check', which passes. After a brief pause, they run 'commit' but receive the error: 'commit failed: configuration database modified by another user. Please reload the configuration and try again.' The engineer is the only person currently logged into the device, but they know that another engineer was working on the same device earlier and may have left a commit pending. What is the most likely reason for the commit failure?

A.The other engineer committed their changes between the commit check and the commit.
B.The commit check did not validate the syntax of the new changes.
C.The candidate configuration has timed out and must be re-entered.
D.The device has insufficient storage to write the new configuration.
AnswerA

This is the most likely cause of the 'configuration database modified by another user' error.

Why this answer

Option A is correct because the error message 'configuration database modified by another user' indicates that another user (the earlier engineer) had a pending commit that was not yet applied or discarded. When the current engineer ran 'commit check', it validated the candidate configuration against the current active configuration, but between that check and the actual 'commit', the other engineer's pending commit was applied (or their session was closed, causing their changes to be committed automatically if they had left a commit pending). This changed the configuration database, causing the commit to fail due to a version mismatch.

Exam trap

The trap here is that candidates may assume 'commit check' passes guarantee a successful commit, but they overlook that the configuration database can be modified by another user between the check and the commit, leading to a commit failure even when no other user is currently logged in.

How to eliminate wrong answers

Option B is wrong because 'commit check' does validate the syntax of the candidate configuration; if it passes, the syntax is correct. Option C is wrong because the candidate configuration does not 'time out' in Junos; it remains in the candidate database until explicitly committed or discarded. Option D is wrong because insufficient storage would typically produce a different error (e.g., 'no space left on device') and is not related to the 'configuration database modified by another user' message.

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4
Multi-Selectmedium

Which TWO commands can be used to view the current active configuration on a Junos device? (Choose two.)

Select 2 answers
A.show configuration | display set
B.show system configuration
C.show configuration
D.show | compare
E.show interfaces
AnswersA, C

Displays the active configuration in set command format.

Why this answer

Option A is correct because the 'show configuration | display set' command displays the active configuration in a set-based format, which is a valid way to view the current active configuration on a Junos device. Option C is correct because the 'show configuration' command directly displays the active configuration in hierarchical format, which is the primary method to view the running configuration.

Exam trap

The trap here is that candidates confuse 'show configuration' with 'show system configuration' (which does not exist) or mistakenly think 'show | compare' shows the active configuration, when it actually shows differences between configurations.

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5
MCQmedium

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

A.rollback 0
B.load override
C.reload
D.commit check
AnswerA

rollback 0 replaces the candidate with the active configuration.

Why this answer

Option A is correct because '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.

Exam trap

The trap here is that Cisco engineers often confuse 'reload' (a Cisco command to reboot) with Junos 'rollback', or mistakenly think 'load override' is the correct way to revert to the last committed configuration, when in fact 'load override' requires a specific file and does not automatically target the last committed state.

How to eliminate wrong answers

Option B is wrong because 'load override' replaces the entire candidate configuration with the contents of a specified file, but it does not automatically revert to the last committed configuration; it loads whatever file is specified, which may not be the last committed one. Option C is wrong because 'reload' is not a valid Junos command; it is a Cisco IOS command that reboots the device, not something used to discard uncommitted changes in configuration mode. Option D is wrong because 'commit check' validates the syntax of the candidate configuration without committing it; it does not discard any changes, so uncommitted edits remain in place.

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6
MCQmedium

A technician is troubleshooting a routing issue and needs to see real-time updates of BGP prefixes being received. Which command should be used?

A.monitor route bgp
B.monitor traffic interface ge-0/0/0
C.show route advertising-protocol bgp
D.show route protocol bgp
AnswerA

Correctly displays real-time BGP route changes.

Why this answer

Option A is correct because the 'monitor route bgp' command in Junos OS provides a real-time, continuously updated view of BGP routes as they are learned or withdrawn. Unlike static show commands, this monitor command refreshes the output dynamically, making it ideal for observing live BGP prefix updates during troubleshooting.

Exam trap

The trap here is that candidates familiar with Cisco IOS often expect a 'debug ip bgp updates' equivalent, but Junos uses 'monitor route bgp' for real-time BGP route updates, while 'monitor traffic' is for packet-level analysis, not routing protocol events.

How to eliminate wrong answers

Option B is wrong because 'monitor traffic interface ge-0/0/0' captures raw packet headers on the interface, not BGP route table updates; it shows traffic flows, not routing protocol prefix changes. Option C is wrong because 'show route advertising-protocol bgp' displays routes that the local router is advertising to a specific BGP peer, not routes being received in real time. Option D is wrong because 'show route protocol bgp' shows a static snapshot of the current BGP route table, not a live, updating feed of incoming prefixes.

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7
Multi-Selecthard

Which TWO statements are true about commit operations in Junos? (Choose two.)

Select 2 answers
A.The rollback 0 command will cause a system reboot.
B.The commit command requires the candidate configuration to be syntactically correct.
C.The commit confirmed command will automatically revert to the previous configuration if not confirmed within the default 10 minutes.
D.The commit check command applies the configuration to the running system.
E.The commit at command is used to schedule a system reboot.
AnswersB, C

Commit will fail if there are syntax errors.

Why this answer

Option B is correct because the `commit` command in Junos requires the candidate configuration to pass syntax and commit script checks before it is applied to the running system. If the configuration contains errors, the commit will fail, ensuring that only valid configurations are activated.

Exam trap

The trap here is confusing `commit confirmed` with a simple commit, or assuming that `rollback 0` triggers a reboot, which is a common misconception from other network operating systems where rollback might involve a reload.

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8
MCQmedium

Refer to the exhibit. An administrator needs to ensure that all emergency (emerg) messages are logged to the console. Based on the configuration shown, which statement is correct?

A.Emergency messages are logged to the console only.
B.Emergency messages are logged to all destinations.
C.Emergency messages are logged only to the file 'messages'.
D.Emergency messages are logged only to the remote host.
AnswerB

Correct; the console includes emerg (since 'any warning' includes more severe levels), the file includes any any, and the remote host includes critical and above, which includes emerg.

Why this answer

Option B is correct because the configuration shown includes the 'any' facility and 'emerg' severity for the console, file, and remote host destinations. In JUNOS, when a severity level is set for a syslog destination, all messages of that severity and higher are logged. Since 'emerg' is the highest severity, it applies to all configured destinations, not just one.

Exam trap

The trap here is that candidates may assume that configuring 'emerg' for a specific destination limits logging to that destination, but in JUNOS, the severity level applies independently to each destination, and all destinations with that severity configured will receive the messages.

How to eliminate wrong answers

Option A is wrong because the configuration explicitly defines syslog destinations for console, file, and remote host, so emergency messages are not limited to the console only. Option C is wrong because the file destination is configured with 'any emerg', meaning emergency messages are logged to the file, but they are also logged to other destinations. Option D is wrong because the remote host is configured with 'any emerg', but emergency messages are not logged only to the remote host; they are logged to all destinations.

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9
MCQhard

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?

A.commit confirmed 10
B.commit at 10
C.set system commit timer 10
D.commit check
AnswerA

Commit confirmed with a timeout ensures rollback if not confirmed.

Why this answer

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.

Exam trap

The trap here is confusing the `commit confirmed` timer with the `commit at` scheduling feature, which sets an absolute time for a commit rather than a countdown for automatic rollback.

How to eliminate wrong answers

Option B is wrong because `commit at 10` schedules a commit to occur at the 10th minute of the hour, not a 10-minute confirmation timer. Option C is wrong because `set system commit timer 10` is not a valid Junos command; there is no such configuration statement. Option D is wrong because `commit check` only validates the syntax of the candidate configuration without committing it, so it cannot initiate a confirmed commit or automatic rollback.

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10
MCQeasy

A user wants to ensure that a configuration change is applied across both Routing Engines in a dual-RE system. Which command must be used?

A.commit and-quit
B.commit confirmed
C.commit full
D.commit synchronize
AnswerD

Correctly applies the commit to both Routing Engines.

Why this answer

Option D is correct because the 'commit synchronize' command applies the candidate configuration to both Routing Engines simultaneously in a dual-RE system. This ensures configuration consistency across the master and backup RE, which is critical for high availability and seamless failover in Junos.

Exam trap

The trap here is that candidates often confuse 'commit synchronize' with 'commit full' or 'commit confirmed', assuming any commit command applies to both REs, but only 'commit synchronize' explicitly ensures dual-RE consistency.

How to eliminate wrong answers

Option A is wrong because 'commit and-quit' is used to commit the configuration and exit the configuration mode, but it does not synchronize changes to the backup RE. Option B is wrong because 'commit confirmed' is used to roll back a commit automatically if not confirmed within a specified time (for safe testing), not for synchronizing across REs. Option C is wrong because 'commit full' forces a full commit of the entire configuration, but it does not inherently synchronize to the backup RE; it is used to rebuild the configuration database from scratch.

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11
MCQmedium

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?

A.| display inheritance
B.| display set
C.| display xml
D.| count
AnswerB

Produces 'set' commands that can be directly pasted into another Junos device.

Why this answer

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.

Exam trap

The trap here is that candidates familiar with Cisco IOS often expect 'show running-config' to output pasteable commands, but Junos requires the explicit '| display set' modifier to achieve the same effect, leading them to choose '| display xml' or '| display inheritance' due to unfamiliarity with Junos output modifiers.

How to eliminate wrong answers

Option A is wrong because '| display inheritance' shows inherited configuration data from groups or hierarchy levels, not a pasteable command format. Option C is wrong because '| display xml' outputs the configuration in XML format, which is not directly executable as CLI commands. Option D is wrong because '| count' simply counts the number of lines in the output, providing no configuration reproduction capability.

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12
MCQeasy

Refer to the exhibit. What does this command accomplish?

A.Displays help for syslog messages that include 'error'.
B.Displays all syslog messages.
C.Displays syslog messages containing the word 'error'.
D.Displays the error log file.
AnswerA

The 'help syslog messages' command provides descriptions of syslog message types; the pipe filters to those with 'error' in the description.

Why this answer

The command 'show log messages | match error' uses a pipe to filter the output of the 'show log messages' command, displaying only lines that contain the string 'error'. However, the question asks what the command accomplishes, and the correct answer is A because the '| match' filter is essentially a help mechanism to find relevant syslog messages, and the exhibit likely shows 'show log messages | match error' which is a common way to display help for syslog messages that include 'error'. The command does not display all syslog messages (B), does not display only messages containing the word 'error' as a whole word (C), and does not display an error log file (D).

Exam trap

The trap here is that candidates often assume 'match error' performs a whole-word search or that there is a dedicated error log file, when in reality it is a substring match on the default messages log file.

How to eliminate wrong answers

Option B is wrong because 'show log messages' alone displays all syslog messages, but the pipe with 'match error' filters the output, so it does not display all messages. Option C is wrong because the 'match' filter performs a substring match, not a whole-word match; it would also match messages containing 'error' as part of a larger word (e.g., 'error-handling'), so it does not strictly display only messages containing the word 'error'. Option D is wrong because there is no separate 'error log file' in Junos; syslog messages are stored in the messages log file, and this command filters that file, not a dedicated error log.

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13
MCQeasy

An administrator wants to navigate to the configuration mode to make changes to the device. Which command should be used?

A.set
B.edit
C.configure
D.cli
AnswerC

Enters configuration mode.

Why this answer

The correct command to enter configuration mode on a Juniper device is 'configure'. This command transitions the CLI from operational mode to configuration mode, allowing the administrator to make changes to the device's configuration. In JUNOS, the CLI has two distinct modes: operational mode (for monitoring and troubleshooting) and configuration mode (for modifying the active or candidate configuration).

Exam trap

The trap here is that Cisco engineers often confuse 'configure terminal' (Cisco IOS) with JUNOS commands, mistakenly thinking 'set' or 'edit' are the entry points to configuration mode, when in fact 'configure' is the required command to enter configuration mode from operational mode.

How to eliminate wrong answers

Option A is wrong because 'set' is a configuration mode command used to add or modify configuration statements, not a command to enter configuration mode itself. Option B is wrong because 'edit' is a configuration mode command that navigates to a specific hierarchy level within the configuration, not a command to enter configuration mode from operational mode. Option D is wrong because 'cli' is used to access the JUNOS CLI from the shell or to restart the CLI process, not to enter configuration mode.

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14
Drag & Dropmedium

Arrange the steps to perform a system backup (snapshot) on a Junos device.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps
Order

Why this order

Snapshot creates a bootable backup of the Junos system. The steps are straightforward.

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15
MCQeasy

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

A.show interfaces terse ge-0/0/1
B.show configuration interfaces ge-0/0/1
C.monitor interface ge-0/0/1
D.show interface ge-0/0/1
AnswerA

Shows operational status in concise format.

Why this answer

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.

Exam trap

The trap here is that Cisco engineers often expect 'show interface' (singular) to work, but Junos strictly requires the plural 'interfaces' for operational commands, and candidates may confuse 'show configuration' (which shows config) with 'show interfaces terse' (which shows operational status).

How to eliminate wrong answers

Option B is wrong because 'show configuration interfaces ge-0/0/1' displays the configured settings for the interface, not its current operational status; it shows what is configured, not whether the interface is up or down. Option C is wrong because 'monitor interface ge-0/0/1' is used for real-time, continuous monitoring of interface statistics and traffic, not for a single snapshot of operational status. Option D is wrong because 'show interface ge-0/0/1' is not a valid Junos command; the correct syntax uses the plural 'interfaces' (e.g., 'show interfaces ge-0/0/1'), and this option omits the 's', which would result in a CLI error.

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16
MCQmedium

An administrator is in configuration mode and wants to see only the interfaces configuration block while editing. Which command will display just that section?

A.show interfaces
B.show
C.display set | match interfaces
D.run show interfaces
AnswerA

'show interfaces' in configuration mode shows the interfaces configuration block.

Why this answer

Option A is correct because in Junos configuration mode, the 'show interfaces' command displays only the interfaces configuration block without leaving configuration mode. This is a Junos-specific feature where 'show' commands within configuration mode show the current candidate configuration, not operational state. The command filters the output to show only the 'interfaces' hierarchy, allowing the administrator to review just that section.

Exam trap

The trap here is that candidates familiar with Cisco IOS might expect 'show running-config | section interfaces' or 'show run interface' and mistakenly choose 'run show interfaces' (Option D), which in Junos shows operational state, not configuration, or they might think 'show' alone (Option B) is sufficient, not realizing it shows the entire configuration from the current level.

How to eliminate wrong answers

Option B is wrong because 'show' alone displays the entire candidate configuration from the current hierarchy level, not just the interfaces block, which would be too verbose if the administrator is at the top of the configuration tree. Option C is wrong because 'display set | match interfaces' is a valid pipe filter but 'display set' is a configuration mode command that converts the configuration to set format; however, the correct syntax would be 'show | display set | match interfaces', and the option as written is incomplete and would not work as intended. Option D is wrong because 'run show interfaces' executes the operational mode command 'show interfaces', which displays the current operational status of interfaces (like link state, IP addresses), not the configuration block, and it temporarily exits configuration mode to run the command.

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17
MCQeasy

A technician needs to display the contents of a configuration file stored on the device's hard disk. Which operational mode command should they use?

A.show configuration
B.file show
C.file list
D.view file
AnswerB

file show displays the contents of a specified file.

Why this answer

The 'file show' command in Junos operational mode is used to display the contents of a file stored on the device's hard disk, such as a configuration file. Unlike 'show configuration', which displays the active candidate or committed configuration, 'file show' reads the raw file from the filesystem, making it the correct choice for viewing a stored configuration file.

Exam trap

The trap here is that candidates often confuse 'show configuration' with viewing a file on disk, but 'show configuration' only shows the configuration from the system's operational database, not the raw file contents stored on the hard disk.

How to eliminate wrong answers

Option A is wrong because 'show configuration' displays the active or candidate configuration from the system's configuration database, not the raw contents of a file on the hard disk. Option C is wrong because 'file list' only lists the names of files in a directory, not their contents. Option D is wrong because 'view file' is not a valid Junos operational mode command; the correct syntax is 'file show'.

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18
MCQmedium

A network administrator has made several configuration changes and now wants to revert all uncommitted changes back to the last committed configuration. Which command should they use?

A.rollback 1
B.load override terminal
C.commit check
D.rollback 0
AnswerD

rollback 0 reverts to the most recent committed configuration.

Why this answer

The 'rollback 0' command reverts all uncommitted changes and restores the active configuration to the last committed configuration. In Junos, candidate configurations are stored in numbered rollback slots (0 being the most recent committed configuration), so 'rollback 0' discards any uncommitted edits and loads the last committed state.

Exam trap

The trap here is that candidates confuse 'rollback 0' with 'rollback 1', mistakenly thinking that 'rollback 1' reverts to the last committed configuration, when in fact 'rollback 0' is the correct slot for the most recent committed state.

How to eliminate wrong answers

Option A is wrong because 'rollback 1' loads the configuration from the second most recent committed configuration (rollback slot 1), not the last committed one, so it would revert to an older committed state rather than discarding uncommitted changes. Option B is wrong because 'load override terminal' replaces the entire candidate configuration with text entered via terminal, which is used for merging or replacing configurations, not for reverting uncommitted changes. Option C is wrong because 'commit check' validates the syntax and semantics of the candidate configuration without committing it, so it does not revert any changes.

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19
MCQhard

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?

A.The protocol icmp is not correct; it should be 'icmp6'.
B.The filter is not applied to any interface.
C.The term 'then reject' should be 'then discard'.
D.The filter must be applied under the 'edit firewall' hierarchy.
AnswerB

A firewall filter must be applied to an interface to take effect.

Why this answer

Option B is correct because 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.

Exam trap

The trap here is that candidates often assume configuring a firewall filter under the 'edit firewall' hierarchy automatically activates it, similar to Cisco IOS where ACLs are applied globally or to interfaces with separate commands, but Junos requires explicit interface application for the filter to process traffic.

How to eliminate wrong answers

Option A is wrong because 'protocol icmp' is correct for IPv4 ICMP; 'icmp6' is used for IPv6 ICMP, which is not relevant here. Option C is wrong because 'then reject' is a valid action that drops packets and sends an ICMP unreachable message; 'then discard' would also drop packets but without notification, and the issue is not about the action type. Option D is wrong because the 'edit firewall' hierarchy is the correct location for configuring firewall filters; the problem is the filter is not applied to an interface, not that it is configured in the wrong place.

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20
MCQmedium

Refer to the exhibit. An administrator sees the following configuration output. What is the purpose of the 'description' statement in this context?

A.It sets the SNMP ifAlias to the interface's MAC address.
B.It sets the administrative comment visible in the config.
C.It sets the interface description visible in 'show interfaces description'.
D.It sets the interface's syslog tag.
AnswerC

Correct; the description appears in the output of 'show interfaces description' and sets the ifAlias SNMP object.

Why this answer

In Junos, the 'description' statement under an interface configuration sets a text string that is displayed in the output of 'show interfaces description'. This is the standard way to provide a human-readable label for the interface, such as 'Link to Core Router A'. It does not affect SNMP, administrative comments, or syslog tags.

Exam trap

The trap here is that candidates often confuse the 'description' statement with the SNMP ifAlias or administrative comments, assuming they serve the same purpose as in other vendors' syntax, but Junos explicitly separates these functions.

How to eliminate wrong answers

Option A is wrong because the SNMP ifAlias is set by the 'snmp ifAlias' statement, not by the 'description' statement; the description does not automatically populate the MAC address. Option B is wrong because the 'description' statement is not an administrative comment; administrative comments in Junos are added using the 'annotate' command or inline comments with '/* ... */'. Option D is wrong because the 'description' statement does not set a syslog tag; syslog tags are configured under the 'syslog' hierarchy or via structured syslog messages.

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21
MCQmedium

Refer to the exhibit. The interface ge-0/0/0 is configured as shown, but the interface is operationally down. Which command would provide the most detailed information about the interface status and errors?

A.show interfaces ge-0/0/0
B.show configuration interfaces ge-0/0/0
C.show interfaces ge-0/0/0 terse
D.show interfaces ge-0/0/0 extensive
AnswerD

This provides the most detailed interface information, including errors.

Why this answer

Option C is correct because `show interfaces extensive` provides detailed operational status, including error counters, physical state, and protocol information. Option A only shows a brief summary. Option B shows basic information but not as detailed as extensive.

Option D shows the configuration, not operational status.

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22
MCQmedium

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?

A.An error message is displayed, and no changes are made.
B.The IP address is configured successfully.
C.The command is queued for later execution.
D.The CLI automatically switches to configuration mode.
AnswerA

set commands are invalid in operational mode, producing an error.

Why this answer

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.

Exam trap

The trap here is that candidates accustomed to Cisco IOS, where 'configure terminal' is not required for every command and some configuration commands can be entered from privileged EXEC mode, mistakenly assume Junos behaves similarly, leading them to expect the command to succeed or the CLI to auto-switch modes.

How to eliminate wrong answers

Option B is wrong because the command is not executed; Junos strictly separates operational and configuration modes, and 'set' is not a valid operational command. Option C is wrong because Junos does not queue configuration commands for later execution; it either rejects them immediately or, if in configuration mode, applies them to the candidate configuration. Option D is wrong because the CLI does not automatically switch modes; the engineer must explicitly enter configuration mode using the 'configure' command.

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23
Multi-Selecthard

Which TWO statements are true about the 'commit confirmed' command? (Choose two.)

Select 2 answers
A.It is used to schedule a commit at a future time.
B.The default timeout is 10 minutes.
C.It saves the configuration to a file before applying.
D.The timeout can be set only in multiples of 5 minutes.
E.It requires a confirmation within the specified time to make the commit permanent.
AnswersB, E

The default timeout is 10 minutes if not specified.

Why this answer

Option B is correct because the default timeout for the 'commit confirmed' command in Junos is 10 minutes. If no confirmation commit is issued within that period, the system automatically rolls back to the previous configuration, ensuring network stability during remote changes.

Exam trap

The trap here is confusing 'commit confirmed' with 'commit at' (scheduling) or assuming the timeout is restricted to 5-minute increments, when in fact it accepts any integer minute value.

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24
MCQmedium

A network engineer wants to view the OSPF log entries in real time. They type 'show log messages | match ospf' and get output, but it does not update. What should they do to see real-time updates of OSPF log entries?

A.Use 'monitor start messages | match ospf'
B.Use 'show log messages | tail'
C.Use 'monitor traffic interface ge-0/0/0'
D.Use 'request system syslog'
AnswerA

This command monitors the messages file in real time and filters for OSPF entries.

Why this answer

Option A is correct because the 'monitor start messages' command in Junos OS enables real-time streaming of syslog messages to the terminal, similar to 'tail -f' on a log file. Piping the output through '| match ospf' filters the live feed to show only OSPF-related entries. In contrast, 'show log messages' is a one-time snapshot that does not update automatically.

Exam trap

The trap here is that candidates familiar with Cisco IOS may confuse 'show log' (which in Cisco can be used with 'monitor' for real-time output) with Junos 'show log', which is static, and overlook the Junos-specific 'monitor start' command for live log streaming.

How to eliminate wrong answers

Option B is wrong because 'show log messages | tail' only displays the last few lines of the static log file and does not provide real-time updates; it is still a one-time command. Option C is wrong because 'monitor traffic interface ge-0/0/0' captures raw packet headers on the interface, not OSPF log entries from the syslog messages file. Option D is wrong because 'request system syslog' is used to configure syslog settings (e.g., remote logging) and does not display log entries in real time.

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25
MCQeasy

Refer to the exhibit. An engineer wants to revert to the configuration from January 14. Which rollback number should they use?

A.load override 2
B.rollback 2
C.rollback 0
D.rollback 1
AnswerD

Rollback 1 corresponds to the second commit (Jan 14).

Why this answer

The rollback command in Junos reverts the candidate configuration to a previously committed configuration. The rollback numbers are indexed from 0 (the most recent commit) to 49 (the oldest). Since the engineer wants to revert to the configuration from January 14, and the most recent commit (rollback 0) is from January 15, rollback 1 corresponds to the January 14 configuration.

Therefore, option D is correct.

Exam trap

The trap here is that candidates often confuse rollback 0 with the current active configuration, but rollback 0 is actually the most recent commit, not the running configuration; they may also mistakenly think rollback 1 is the oldest, when in fact rollback 49 is the oldest saved configuration.

How to eliminate wrong answers

Option A is wrong because 'load override 2' is not a valid Junos command; the correct command is 'rollback 2' to load a previous configuration, and 'load override' is used to replace the candidate configuration with a file, not a rollback number. Option B is wrong because 'rollback 2' would revert to the configuration two commits before the most recent one, which would be from January 13, not January 14. Option C is wrong because 'rollback 0' reverts to the most recently committed configuration (January 15), which is not the desired date.

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26
Multi-Selectmedium

An engineer needs to view the current operational state of the device, including system uptime, CPU load, and memory usage. Which two commands would provide this information? (Choose two.)

Select 2 answers
A.show system processes
B.show system uptime
C.show system storage
D.show system memory
E.show chassis hardware
AnswersB, D

Displays system uptime and load averages (CPU).

Why this answer

The 'show system uptime' command displays the system uptime, load averages, and current time, which directly provides the uptime and CPU load information. The 'show system memory' command shows memory usage statistics, including total, used, and available memory. Together, these two commands fulfill the requirement to view the current operational state including system uptime, CPU load, and memory usage.

Exam trap

The trap here is that candidates often confuse 'show system processes' with providing CPU load averages and memory totals, when in fact it only shows per-process statistics and not the aggregate system load or overall memory usage.

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27
MCQmedium

A network administrator accidentally deleted a vital part of the configuration while in configuration mode. They need to revert to the previous configuration without losing recent changes that are correct. Which action should they take?

A.deactivate
B.rollback 1
C.delete
D.rollback 0
AnswerB

Reverts to the configuration from the previous commit, discarding uncommitted changes.

Why this answer

Option B is correct because the 'rollback 1' command reverts the candidate configuration to the most recently committed configuration (the previous active configuration), while preserving any uncommitted changes that were made after the rollback. This allows the administrator to discard the accidental deletion and then manually re-apply only the correct recent changes before committing.

Exam trap

The trap here is that candidates often confuse 'rollback 0' (which reverts to the current active config, discarding all uncommitted changes) with 'rollback 1' (which reverts to the previous committed config, preserving uncommitted changes), leading them to choose option D instead of B.

How to eliminate wrong answers

Option A is wrong because 'deactivate' disables a configuration statement without removing it, but it does not revert the configuration to a previous state; it only suppresses the active effect of the specified statement. Option C is wrong because 'delete' removes configuration statements from the candidate configuration, which would worsen the situation by further deleting parts of the configuration. Option D is wrong because 'rollback 0' reverts to the current active configuration (the one that was last committed), which would discard all uncommitted changes, including any correct recent modifications the administrator wants to keep.

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28
MCQhard

A junior admin tries to commit a configuration but receives a 'commit error: syntax error' message. They suspect a missing closing brace. Which CLI command helps identify the exact line with the error?

A.commit check
B.rollback 0
C.load merge
D.show configuration
AnswerA

Validates the candidate configuration and reports syntax errors with exact line numbers.

Why this answer

The 'commit check' command validates the candidate configuration for syntax errors without committing it. When a syntax error like a missing closing brace is present, commit check outputs the exact line number and file where the error occurs, allowing the admin to locate and fix the issue before attempting a commit again.

Exam trap

The trap here is that candidates may confuse 'show configuration' with a validation tool, not realizing it only displays the configuration text without any syntax checking, whereas 'commit check' is the dedicated command for identifying syntax errors before commit.

How to eliminate wrong answers

Option B is wrong because 'rollback 0' reverts the candidate configuration to the last committed configuration, which does not help identify the syntax error line. Option C is wrong because 'load merge' is used to merge a configuration file into the candidate configuration, not to validate syntax or pinpoint errors. Option D is wrong because 'show configuration' displays the current candidate configuration but does not perform syntax validation or highlight error lines.

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29
Multi-Selectmedium

Which TWO statements about the 'commit' operation in Junos OS are correct?

Select 2 answers
A.It can be rolled back using the 'rollback 0' command.
B.It applies the candidate configuration to the active configuration.
C.It saves the configuration to the juniper.conf.gz file.
D.It automatically reboots the device if system changes are made.
E.It requires the configuration to be validated with 'commit check' first.
AnswersB, C

This is the primary function of commit.

Why this answer

Option B is correct because the 'commit' operation in Junos OS applies the candidate configuration to the active configuration, making the changes effective immediately. This is the fundamental purpose of the commit command, which activates the pending configuration changes stored in the candidate configuration database.

Exam trap

The trap here is that candidates often confuse 'rollback 0' with a commit rollback, not realizing that rollback operates on the candidate configuration before commit, while 'rollback 0' reverts to the last committed configuration in the candidate database, not undoing a commit that has already been applied.

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30
MCQmedium

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

A.Enables IPv6.
B.Sets the MTU.
C.Defines a physical interface.
D.Defines a logical interface.
AnswerD

'unit' is used to create logical interfaces on a physical interface.

Why this answer

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.

Exam trap

The trap here is that candidates familiar with Cisco IOS might assume 'unit 0' is a physical interface or a default MTU setting, but in Junos, the unit number always defines a logical interface, and physical interfaces are configured separately without a unit keyword.

How to eliminate wrong answers

Option A is wrong because 'unit 0' does not enable IPv6; IPv6 is enabled by configuring a family inet6 address under the logical unit, not by the unit number itself. Option B is wrong because the MTU is set using the 'mtu' statement at the physical interface level (e.g., 'set interfaces ge-0/0/0 mtu 1500'), not by the 'unit 0' statement. Option C is wrong because a physical interface is defined by the interface name (e.g., ge-0/0/0), not by the 'unit' statement; 'unit 0' creates a logical subinterface on top of that physical interface.

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31
MCQeasy

A technician wants to view the system log messages in real time. Which command should they use?

A.show system log
B.monitor start messages
C.start shell
D.show log messages
AnswerB

Displays system log messages in real time.

Why this answer

The 'monitor start messages' command is used in Junos OS to display system log messages in real time as they are generated. This is the correct command for live monitoring of system events, similar to 'tail -f' on Unix systems.

Exam trap

The trap here is that candidates familiar with Cisco IOS might expect 'show log' or 'show logging' to provide real-time output, but in Junos, 'show log messages' only shows the static file, while 'monitor start messages' is the live tail command.

How to eliminate wrong answers

Option A is wrong because 'show system log' is not a valid Junos command; the correct command to view stored logs is 'show log messages'. Option C is wrong because 'start shell' drops the user into a Unix shell environment, not a real-time log viewer. Option D is wrong because 'show log messages' displays the current contents of the messages log file, but does not provide real-time updates; it shows a static snapshot.

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32
MCQeasy

A network administrator needs to view the current configuration but is only interested in the interfaces section. Which CLI command should they use?

A.show configuration interfaces
B.show configuration | display set
C.show interfaces
D.show configuration | match interfaces
AnswerA

Displays only the interfaces configuration block.

Why this answer

Option A is correct because the 'show configuration interfaces' command displays only the interfaces hierarchy from the active candidate configuration. This command directly filters the configuration output to the interfaces stanza, allowing the administrator to view interface-specific settings without extraneous configuration data.

Exam trap

The trap here is that candidates confuse operational commands (like 'show interfaces') with configuration commands (like 'show configuration interfaces'), or they overuse pipe filters like 'match' which can produce incomplete or misleading results due to partial line matches.

How to eliminate wrong answers

Option B is wrong because 'show configuration | display set' converts the entire configuration into a set of configuration mode commands, but it does not filter to show only the interfaces section; it outputs all configuration in set format. Option C is wrong because 'show interfaces' displays operational status and statistics for interfaces, not the configuration; it shows runtime state rather than the configured settings. Option D is wrong because 'show configuration | match interfaces' uses a pipe to grep for lines containing the word 'interfaces', which may include unrelated lines (e.g., references in firewall filters or routing options) and does not reliably isolate the full interfaces configuration block.

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33
Multi-Selectmedium

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

Select 2 answers
A.The pipe (|) can be used to filter command output.
B.The 'edit' command is used in operational mode to navigate the hierarchy.
C.The 'set' command is used in operational mode to set parameters.
D.The 'commit' command applies the candidate configuration.
E.The 'rollback 0' command discards the candidate configuration.
AnswersA, D

The pipe filters output.

Why this answer

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.

Exam trap

The trap here is that candidates often confuse the use of 'edit', 'set', and 'rollback' commands between operational and configuration modes, mistakenly thinking they can be used interchangeably, when in fact they are strictly mode-specific.

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34
MCQhard

A senior network administrator is logged into a Juniper device in operational mode. They need to make a configuration change to the BGP group 'INTERNAL'. They type 'configure terminal' and receive 'unknown command'. They then type 'configure' and enter configuration mode. They make the needed changes and exit configuration mode using 'exit'. They then try to view the active configuration to verify the changes by typing 'show configuration | match INTERNAL'. They see no output. What is the most likely reason?

A.The command 'show configuration' only shows the candidate configuration, not the active.
B.They exited configuration mode without committing, so the changes were lost.
C.They should have used 'commit' before exiting configuration mode.
D.They need to be in configuration mode to run 'show configuration'.
AnswerC

Commit activates the changes; without commit, the active configuration is unchanged.

Why this answer

Option C is correct because in Junos, configuration changes made in configuration mode are stored in a candidate configuration until explicitly committed using the 'commit' command. Exiting configuration mode with 'exit' without committing discards all uncommitted changes, so the BGP group 'INTERNAL' modification never became part of the active configuration. The 'show configuration' command displays the active (committed) configuration, which explains why no output matching 'INTERNAL' was seen.

Exam trap

The trap here is that candidates familiar with Cisco IOS expect 'exit' to save changes or that 'show running-config' shows uncommitted changes, but Junos requires an explicit 'commit' to activate changes, and 'show configuration' only reflects the committed state.

How to eliminate wrong answers

Option A is wrong because 'show configuration' in operational mode displays the active (committed) configuration, not the candidate configuration; the candidate configuration is viewed with 'show | compare' or by being in configuration mode. Option B is wrong because exiting configuration mode without committing does not automatically lose changes—the candidate configuration persists until explicitly discarded with 'rollback' or overridden, but the changes are not active until committed; however, the question states they exited and then ran 'show configuration', which shows the active config, so the changes were effectively not visible because they were never committed. Option D is wrong because 'show configuration' can be run from operational mode (it is a valid operational command) and does not require being in configuration mode.

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35
Multi-Selecteasy

Which two commands can be used to view the candidate configuration in set format? (Choose two.)

Select 2 answers
A.show configuration | display set | no-parenthesis
B.show | set
C.show | display set (in configuration mode)
D.show configuration | display set (in operational mode)
E.show configuration | display inherited
AnswersC, D

This command displays the candidate configuration in set format from configuration mode.

Why this answer

Option C is correct because in configuration mode, the 'show | display set' command outputs the candidate configuration as a series of 'set' commands, which is a compact and script-friendly format. Option D is also correct because the same output can be achieved in operational mode using 'show configuration | display set', which displays the candidate configuration from the operational CLI context.

Exam trap

The trap here is that candidates confuse the 'display set' modifier with the 'set' command or assume that 'show | set' is a valid shortcut, when in fact the correct syntax requires the pipe to 'display set' and the command must be issued in the appropriate mode (configuration or operational with 'show configuration').

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36
Multi-Selecteasy

Which TWO statements about the Junos CLI are correct?

Select 2 answers
A.The `commit confirmed` command saves the configuration permanently.
B.The pipe character (|) can be used to filter command output.
C.The `run` command allows operational mode commands to be executed from configuration mode.
D.The `set cli screen-length 0` command disables command-line editing features.
E.The `rollback 0` command reverts to the previous committed configuration.
AnswersB, C

This is a standard Junos CLI feature for filtering output.

Why this answer

Option A is correct because the pipe character filters output in operational mode. Option D is correct because the `run` command allows executing operational commands from configuration mode. Option B is wrong because `commit confirmed` requires a subsequent commit to make changes permanent.

Option C is wrong because `rollback 0` reverts to the current active configuration, not the previous one. Option E is wrong because `set cli screen-length 0` disables paging, not command-line editing.

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37
MCQeasy

A network administrator wants to quickly review only the parts of the Junos configuration that differ from the factory defaults, to identify custom settings. Which command is most appropriate?

A.show configuration | no-more
B.show configuration
C.show configuration | display omit
D.show | compare
AnswerC

Correctly omits default configuration statements, showing only non-default settings.

Why this answer

Option C is correct because the 'display omit' pipe modifier filters out configuration statements that match the factory-default values, showing only the lines that differ from the defaults. This allows the administrator to quickly review custom settings without manually comparing against a baseline.

Exam trap

The trap here is that candidates often confuse 'display omit' with 'display set' or 'show | compare', mistakenly thinking that comparing candidate vs. active configuration is the same as filtering out factory defaults.

How to eliminate wrong answers

Option A is wrong because 'show configuration | no-more' simply disables the pager output but still displays the entire configuration, including all default settings. Option B is wrong because 'show configuration' outputs the full active configuration without any filtering, requiring manual inspection to identify custom settings. Option D is wrong because 'show | compare' compares the candidate configuration against the active configuration, not against factory defaults, and is used to review pending changes before commit.

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38
MCQhard

Refer to the exhibit. An engineer configures a new IPv6 address on ge-0/0/0 unit 0 by entering the following commands in configuration mode: set interfaces ge-0/0/0 unit 0 family inet6 address 2001:db8::2/64 commit After the commit, the engineer runs 'show interfaces terse ge-0/0/0' and sees only the two original addresses. What is the most likely cause?

A.The engineer used 'commit' instead of 'commit confirmed'.
B.The engineer did not enter configuration mode before running the 'set' command.
C.Junos only allows one IPv6 address per interface.
D.The 'set' command requires the 'add' keyword to add a second address.
AnswerB

'set' is a configuration mode command; in operational mode it would be rejected.

Why this answer

Option B is correct because the engineer likely ran the 'set' command from operational mode (e.g., at the '>' prompt) rather than from configuration mode (e.g., at the '#' prompt). In Junos, 'set' commands only take effect when entered in configuration mode; if entered in operational mode, they are silently ignored or produce an error, and the configuration is not modified. Since the engineer saw no new address after commit, the 'set' command was never applied to the candidate configuration.

Exam trap

The trap here is that candidates accustomed to Cisco IOS may assume a 'set' command entered at any prompt modifies the running configuration, but Junos requires explicit entry into configuration mode (via 'configure' or 'edit') for such commands to take effect.

How to eliminate wrong answers

Option A is wrong because 'commit confirmed' is used for automatic rollback if the commit is not confirmed within a timeout; using a regular 'commit' does not prevent address addition. Option C is wrong because Junos supports multiple IPv6 addresses on a single interface (e.g., multiple 'address' statements under 'family inet6'). Option D is wrong because Junos does not require an 'add' keyword; simply specifying a new 'address' statement under the existing 'family inet6' hierarchy adds it without any special keyword.

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39
MCQhard

An operator needs to copy the running configuration to a remote FTP server for backup. Which command accomplishes this?

A.scp /config/juniper.conf.gz user@server:/path
B.copy configuration to ftp://user:pass@server/path
C.ftp put /config/juniper.conf.gz
D.file copy /config/juniper.conf.gz ftp://user:pass@server/path
AnswerD

Correctly copies the configuration file to an FTP server.

Why this answer

Option D is correct because the `file copy` command in Junos is the standard method for transferring files to or from the device, and it supports FTP as a source or destination. The syntax `file copy /config/juniper.conf.gz ftp://user:pass@server/path` correctly specifies the local file path and the remote FTP URL, including credentials and destination path.

Exam trap

The trap here is that candidates familiar with Cisco IOS may expect a command like `copy running-config ftp:` or `ftp put`, but Junos uses a unified `file copy` command with protocol-specific URLs, and the configuration file is stored at `/config/juniper.conf.gz` rather than in a running-config concept.

How to eliminate wrong answers

Option A is wrong because `scp` is not a valid Junos CLI command; file transfers using SCP are performed via the `file copy` command with an `scp://` URL, not a standalone `scp` command. Option B is wrong because `copy configuration` is not a valid Junos command; the correct command to copy the configuration is `file copy`, and the syntax shown does not match Junos CLI conventions. Option C is wrong because `ftp put` is not a Junos CLI command; Junos uses `file copy` with an FTP URL to upload files, and the path `/config/juniper.conf.gz` is correct but the command syntax is invalid.

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40
MCQmedium

An engineer needs to apply a configuration change to the device, but only if the configuration is syntactically correct. Which command should be used before committing?

A.commit
B.commit check
C.commit confirmed
D.show | compare
AnswerB

Validates syntax without committing.

Why this answer

The 'commit check' command validates the candidate configuration for syntax errors without applying it, making it the correct choice when the engineer only wants to verify syntactic correctness before committing. Unlike 'commit', which applies changes immediately, 'commit check' performs the same validation as a commit but stops short of activating the configuration.

Exam trap

The trap here is that candidates confuse 'commit check' with 'commit confirmed', thinking both are safe validation commands, but 'commit confirmed' actually applies the configuration and can cause immediate service impact if the syntax is invalid.

How to eliminate wrong answers

Option A is wrong because 'commit' applies the configuration changes immediately, not just checking syntax; it would activate the changes even if the engineer only wanted validation. Option C is wrong because 'commit confirmed' applies the configuration and sets a rollback timer, which is used for testing changes with automatic rollback, not for a simple syntax check. Option D is wrong because 'show | compare' displays the differences between the candidate and active configurations but does not perform any syntax validation.

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41
MCQhard

You are a junior network engineer at a company that uses Juniper MX routers. You are troubleshooting a connectivity issue on a branch router. The branch router has two upstream links to the corporate network: ge-0/0/0 (10.1.1.1/30, connected to core router A) and ge-0/0/1 (10.1.1.5/30, connected to core router B). The branch router runs OSPF and has a default route learned from both upstream routers. The routing table shows two equal-cost default routes via both next hops. However, traffic from the branch to the corporate network is experiencing intermittent high latency and some packet loss. You suspect that asymmetric routing is causing issues because the return traffic is not following the same path. You want to influence the router to prefer one upstream link for all traffic to the corporate network. You have decided to adjust the OSPF metric on the branch router to make the link to core router A more preferred. You are in configuration mode on the branch router. Which single configuration change will accomplish this goal?

A.set interfaces ge-0/0/1 unit 0 family inet cost 200
B.set protocols ospf area 0 interface ge-0/0/1 passive
C.set protocols ospf area 0 interface ge-0/0/1 metric 200
D.set interfaces lo0 unit 0 family inet address 10.0.0.1/32 metric 100
AnswerC

Increasing the metric on ge-0/0/1 makes it less preferred, so traffic will use ge-0/0/0.

Why this answer

Option C is correct because setting the OSPF metric on interface ge-0/0/1 to a higher value (200) increases the cost of that link, making the default route via ge-0/0/0 (which retains the default OSPF metric of 1 on a Gigabit Ethernet interface) more preferred. This influences the branch router to use the lower-cost path through core router A for all traffic to the corporate network, resolving asymmetric routing issues.

Exam trap

The trap here is that candidates often confuse the 'metric' configuration under the OSPF protocol hierarchy with the 'cost' parameter under interfaces, or mistakenly think that making an interface passive or adjusting loopback metrics will influence OSPF path selection.

How to eliminate wrong answers

Option A is wrong because the 'cost' parameter is not a valid configuration statement under 'set interfaces'; OSPF cost is configured under the OSPF protocol hierarchy, not directly on the interface. Option B is wrong because setting the interface to 'passive' prevents OSPF from sending or receiving hello packets on that interface, which would break OSPF adjacency entirely, rather than simply adjusting path preference. Option D is wrong because the 'metric' statement under the loopback interface is used for static routes or other protocols, not for OSPF interface cost; OSPF uses a cost value derived from interface bandwidth or explicitly set under 'protocols ospf'.

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42
MCQeasy

During a maintenance window, an engineer makes critical changes and wants the configuration to automatically revert if they lose connectivity. Which command should they use before committing?

A.commit
B.commit confirmed
C.commit check
D.commit at
AnswerB

commit confirmed adds a safety net; if not confirmed, it rolls back.

Why this answer

Option B, 'commit confirmed', is correct because it allows the engineer to commit a configuration change with a default 10-minute rollback timer. If the engineer loses connectivity and does not confirm the commit within that period, the system automatically reverts to the previous configuration, ensuring the device remains reachable.

Exam trap

The trap here is that candidates may confuse 'commit confirmed' with 'commit check', thinking syntax validation alone provides safety, or they may assume 'commit at' offers automatic rollback, but neither command includes the confirmation-based rollback mechanism that 'commit confirmed' provides.

How to eliminate wrong answers

Option A is wrong because 'commit' applies the configuration permanently with no automatic rollback, which could leave the device unreachable if the changes break connectivity. Option C is wrong because 'commit check' only validates the syntax of the configuration without committing it, so it does not provide any automatic rollback mechanism. Option D is wrong because 'commit at' schedules a commit at a specific time but does not include a confirmation or automatic rollback feature if connectivity is lost.

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43
Multi-Selectmedium

Which TWO commands can be used to view the current running configuration?

Select 2 answers
A.show configuration | display inheritance
B.show configuration | display set
C.show configuration | match
D.show configuration
E.show configuration | compare
AnswersB, D

Displays the configuration as a series of set commands.

Why this answer

Option B is correct because the 'show configuration | display set' command outputs the current active configuration in 'set' format, which is a flat, line-by-line representation of configuration statements. Option D is correct because 'show configuration' without any pipe modifier displays the entire running configuration in its native hierarchical format. Both commands allow you to view the current running configuration, just in different presentation styles.

Exam trap

The trap here is that candidates confuse pipe modifiers like 'display inheritance' or 'compare' as valid ways to view the current configuration, when in fact they either add inherited data or compare revisions, not display the running config as-is.

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44
MCQhard

After upgrading Junos, a router fails to boot with a file system error. The admin needs to recover the system from the backup partition. Which key should be pressed during boot to access the boot menu?

A.Ctrl+C
B.Esc
C.Enter
D.Space
AnswerD

Correctly invokes the boot loader menu to choose an alternate partition.

Why this answer

Option D is correct because pressing the Space bar during the boot process on a Juniper device interrupts the normal boot sequence and presents the boot menu. From this menu, the administrator can select the backup Junos partition (typically labeled as '1' or 'backup') to recover the system when the primary partition has a file system error.

Exam trap

The trap here is that candidates familiar with Cisco IOS might confuse the Juniper boot menu access (Space bar) with Cisco's Ctrl+Break or other interrupt keys, leading them to select Ctrl+C or Esc incorrectly.

How to eliminate wrong answers

Option A is wrong because Ctrl+C is used to abort the current command in the Junos CLI, not to access the boot menu during system startup. Option B is wrong because the Esc key is not used for boot menu access on Juniper devices; it may be used in other contexts like editing CLI commands. Option C is wrong because pressing Enter during boot simply continues the normal boot process without interrupting it, which would not allow selection of the backup partition.

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45
MCQmedium

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

A.The interface is administratively down.
B.The interface is a loopback interface.
C.The interface has an IPv6 address only.
D.The interface is up and the physical link is up.
AnswerD

Admin up means enabled; Link up means physical connection is active.

Why this answer

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.

Exam trap

The trap here is that candidates may confuse 'Admin up' with 'Link up', thinking one implies the other, or incorrectly assume 'Admin up' alone means the interface is fully operational, when in fact both must be 'up' for traffic to flow.

How to eliminate wrong answers

Option A is wrong because 'Admin up' explicitly indicates the interface is administratively enabled, not down. Option B is wrong because loopback interfaces are virtual (lo0) and do not have physical link states like 'Link up'; they are always logically up unless administratively disabled. Option C is wrong because the presence of an IPv6 address is unrelated to the administrative or link status; an interface can have an IPv6 address and still show 'Admin up' and 'Link up'.

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46
MCQhard

Refer to the exhibit. What does this output indicate?

A.There is a syntax error.
B.The commit succeeded.
C.The configuration is identical.
D.The candidate configuration differs from the active configuration.
AnswerD

The '+' and '-' lines show changes between candidate and active.

Why this answer

The output shows the 'show | compare' command, which displays the differences between the candidate configuration and the active (committed) configuration. The presence of lines prefixed with '+' (additions) and '-' (deletions) indicates that the candidate configuration is not identical to the active configuration, confirming that they differ.

Exam trap

The trap here is that candidates may confuse the 'show | compare' output with a commit confirmation or syntax check, when in fact it only indicates that uncommitted changes exist in the candidate configuration.

How to eliminate wrong answers

Option A is wrong because a syntax error would be reported by the commit check or commit command, not by the 'show | compare' output, which only shows configuration differences. Option B is wrong because a successful commit would make the candidate configuration identical to the active configuration, resulting in no output from 'show | compare'. Option C is wrong because if the configuration were identical, the 'show | compare' command would produce no output (empty), but the exhibit shows lines with '+' and '-', indicating differences.

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47
Multi-Selecthard

Which three statements about JunOS CLI pipe commands are true? (Choose three.)

Select 3 answers
A.The '| match' pipe filter displays lines that match a regular expression.
B.The '| count' pipe filter counts the number of lines in the output.
C.The '| except' pipe filter displays lines that do not match a regular expression.
D.The '| resolve' pipe filter resolves IP addresses to hostnames.
E.The '| display set' pipe filter converts operational output to set format.
AnswersA, B, C

This is a fundamental use of the pipe filter.

Why this answer

Option A is correct because the '| match' pipe filter in JunOS uses a regular expression to display only those lines in the output that contain a match. This is a standard filtering mechanism that allows operators to quickly isolate relevant configuration or operational data without scrolling through entire command output.

Exam trap

The trap here is that candidates often confuse '| resolve' with DNS resolution of addresses in the output, but it only performs reverse lookups and does not modify the output format or filter lines.

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48
MCQeasy

Refer to the exhibit. Based on the output, which statement is true?

A.The admin user has read-only access.
B.The interface ge-0/0/0 has been disabled.
C.The root password is stored in plaintext.
D.The router hostname is router1.
AnswerD

The 'set system host-name router1' line confirms this.

Why this answer

The output shows the system prompt ending with 'router1>', which indicates the hostname is set to 'router1'. In Junos, the CLI prompt format is 'hostname>', so this directly confirms the router hostname. Option D is correct because the prompt explicitly displays 'router1' as the active hostname.

Exam trap

The trap here is that candidates may overlook the CLI prompt as a direct indicator of the hostname and instead look for a 'show configuration' output, but Junos always displays the hostname in the prompt immediately upon login.

How to eliminate wrong answers

Option A is wrong because the prompt 'router1>' indicates a user in operational mode, not read-only access; read-only access would still show the same prompt but with restricted commands, and the output does not show any permission restrictions. Option B is wrong because the interface ge-0/0/0 is not mentioned in the output; the output only shows the CLI prompt, not any interface status or configuration. Option C is wrong because Junos never stores the root password in plaintext; it is always hashed using SHA-512 or MD5, and the output does not display any password.

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49
MCQmedium

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

A.rollback 1
B.rollback 0
C.load override
D.revert
AnswerA

Reverts to the previous committed configuration.

Why this answer

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.

Exam trap

The trap here is that candidates familiar with Cisco IOS may expect a 'revert' command or confuse 'rollback 0' (current config) with the previous commit, leading them to select the wrong rollback number or a non-existent command.

How to eliminate wrong answers

Option B (rollback 0) is wrong because rollback 0 refers to the currently active configuration, not the one before the last commit; using it would load the same configuration already in use. Option C (load override) is wrong because it is used to replace the entire candidate configuration with a configuration from a file or URL, not to revert to a previous commit. Option D (revert) is wrong because 'revert' is not a valid Junos CLI command; the correct command is 'rollback'.

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50
MCQhard

An engineer needs to check if a junos configuration file is syntactically correct before applying it. Which command should be used?

A.load check
B.commit check
C.check commit
D.validate
AnswerB

commit check verifies syntax and semantics of the candidate configuration.

Why this answer

The 'commit check' command validates the syntax and semantics of the candidate configuration without applying it. If errors are found, they are reported, and the configuration is not committed. This allows the engineer to verify correctness before making the change active.

Exam trap

The trap here is that candidates familiar with Cisco IOS may expect a 'validate' command or confuse the order of keywords, but Junos requires the exact syntax 'commit check' for pre-commit validation.

How to eliminate wrong answers

Option A is wrong because 'load check' is not a valid Junos command; the correct syntax for loading a configuration file is 'load merge', 'load override', etc., and 'load check' does not exist. Option C is wrong because 'check commit' reverses the order of the valid command; Junos uses 'commit check' as the standard syntax. Option D is wrong because 'validate' is not a Junos CLI command for checking configuration syntax; the equivalent functionality is provided by 'commit check' or 'commit confirmed'.

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51
MCQmedium

A network engineer needs to view the operational status of all interfaces on a Junos device, including those that are disabled. Which command should be used?

A.show interfaces
B.show configuration interfaces
C.show interfaces terse
D.monitor interface traffic
AnswerC

The 'show interfaces terse' command displays all interfaces in a compact format, including disabled ones.

Why this answer

The 'show interfaces terse' command displays a concise, one-line-per-interface summary of all interfaces, including their administrative status (up/down) and whether they are disabled. Unlike 'show interfaces', which by default only shows interfaces that are physically present and enabled, 'terse' includes interfaces that are administratively disabled (e.g., 'down' in the Admin column). This makes it the correct choice for viewing the operational status of all interfaces, including disabled ones.

Exam trap

The trap here is that candidates often assume 'show interfaces' shows all interfaces, but it only shows enabled interfaces by default, while 'show interfaces terse' explicitly includes disabled interfaces in its output.

How to eliminate wrong answers

Option A is wrong because 'show interfaces' displays detailed information only for interfaces that are physically present and enabled; it does not show interfaces that are administratively disabled unless they are explicitly specified. Option B is wrong because 'show configuration interfaces' displays the configured interface statements from the candidate or active configuration, not the operational status (e.g., up/down, disabled state). Option D is wrong because 'monitor interface traffic' is used for real-time traffic monitoring and statistics, not for viewing the administrative or operational status of interfaces.

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52
MCQhard

During a maintenance window, an engineer needs to apply a configuration change that reverts automatically if the commit fails or the administrator does not confirm within a set time. Which feature should be used?

A.commit confirmed
B.commit check
C.commit synchronize
D.commit at 03:00
AnswerA

Correctly implements automatic rollback if not confirmed within the set time.

Why this answer

The 'commit confirmed' feature allows an engineer to apply a configuration change that automatically reverts to the previous configuration if the commit is not confirmed within a specified time period (default 10 minutes). This ensures that if the commit fails or the administrator loses connectivity, the system rolls back safely without manual intervention.

Exam trap

The trap here is that candidates often confuse 'commit confirmed' with 'commit check' or 'commit synchronize', mistakenly thinking that syntax validation or dual-RE synchronization provides the same automatic rollback safety, but only 'commit confirmed' implements the timed confirmation and automatic revert mechanism.

How to eliminate wrong answers

Option B is wrong because 'commit check' only validates the syntax and semantics of the candidate configuration without actually applying it; it does not provide any automatic rollback or confirmation mechanism. Option C is wrong because 'commit synchronize' is used in a dual-RE (Routing Engine) chassis to apply the configuration to both REs simultaneously, not to provide a timed automatic rollback. Option D is wrong because 'commit at 03:00' schedules the commit to occur at a specific time but does not include a confirmation or automatic rollback feature; once committed, the change persists unless manually reverted.

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53
Multi-Selecthard

Which THREE CLI features are available in Junos OS to assist with command entry?

Select 3 answers
A.? (question mark) for context-sensitive help.
B.Ctrl+R to repeat the last command.
C.Up arrow key to recall previous commands.
D.Ctrl+Z to undo the last command.
E.Tab key for command completion.
AnswersA, C, E

Displays available commands or options.

Why this answer

Option A is correct because the question mark (?) provides context-sensitive help in Junos OS, displaying available commands, options, and syntax at any point in the CLI. This is a fundamental feature for command discovery and verification, especially when the exact command syntax is not known.

Exam trap

The trap here is that candidates familiar with Cisco IOS may mistakenly associate Ctrl+Z with undo functionality (since in IOS it exits configuration mode) or Ctrl+R with repeating commands, but Junos uses different key bindings and relies on the Up arrow and Tab for command recall and completion.

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54
MCQeasy

A junior network engineer is learning JunOS CLI and wants to view the last 10 lines of the system log file. They log into the device and type 'show log messages | last 10'. They receive an error: 'unknown pipe command'. Which pipe command should they use instead?

A.| last 10
B.| display 10
C.| head 10
D.| tail 10
AnswerD

The '| tail' pipe command displays the last N lines of output.

Why this answer

In JunOS CLI, the pipe command to display the last N lines of output is '| tail N', not '| last N'. The 'tail' command filters the output to show only the final lines, analogous to the Unix 'tail' utility. Option D is correct because '| tail 10' will show the last 10 lines of the system log file.

Exam trap

The trap here is that candidates familiar with Cisco IOS may expect '| last 10' to work, but JunOS uses Unix-style pipe commands where 'tail' is the correct filter for displaying the end of output.

How to eliminate wrong answers

Option A is wrong because '| last 10' is not a valid JunOS pipe command; it triggers an 'unknown pipe command' error. Option B is wrong because '| display 10' is not a valid pipe command; 'display' is used for XML or set format output, not for line count filtering. Option C is wrong because '| head 10' would show the first 10 lines, not the last 10, and is the opposite of what the engineer needs.

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55
MCQhard

You are a network engineer for a service provider that recently deployed a Juniper MX router at a new Point of Presence (PoP). The router is used to aggregate customer connections and exchange routes with upstream providers via BGP. After the initial configuration, you notice that the router is not learning any routes from one of the upstream BGP peers. You have verified that the BGP session is established (state Established) and that the peer is sending routes. You suspect that the issue might be related to the firewall filter or routing policy. You want to determine if any inbound routes are being rejected and why. Which command would provide the most direct information about why routes are being rejected?

A.show route protocol bgp
B.show route receive-protocol bgp 192.0.2.1
C.show bgp summary
D.show firewall filter <filter-name>
AnswerB

Displays received routes and indicates if any are rejected by policy.

Why this answer

Option B, 'show route receive-protocol bgp 192.0.2.1', is correct because it displays the exact routes received from a specific BGP peer along with any policy or filter actions applied (e.g., reject, accept). This command directly shows whether routes are being rejected and the reason (e.g., due to an import policy or firewall filter), making it the most direct diagnostic tool for the described issue.

Exam trap

The trap here is that candidates often assume 'show bgp summary' or 'show route protocol bgp' will reveal route rejection details, but they only show aggregated statistics or installed routes, not the per-peer policy decisions that cause routes to be hidden or rejected.

How to eliminate wrong answers

Option A is wrong because 'show route protocol bgp' displays all BGP routes in the routing table, but it does not show why routes were rejected or filtered before installation. Option C is wrong because 'show bgp summary' only shows BGP session state and statistics (e.g., prefixes received), not the specific routes or rejection reasons. Option D is wrong because 'show firewall filter <filter-name>' shows firewall filter counters and rules, but it does not directly correlate to BGP route rejection unless the filter is explicitly applied to the BGP session; it is indirect and less specific than the receive-protocol command.

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56
MCQhard

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?

A.show route table inet.0
B.show route table inet6.0
C.show route forwarding-table
D.show route protocol bgp
AnswerA

Displays IPv4 unicast route table.

Why this answer

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.

Exam trap

The trap here is that candidates often confuse the routing table (RIB) with the forwarding table (FIB), or they may think 'show route protocol bgp' shows all routes, when it only shows routes from a specific protocol.

How to eliminate wrong answers

Option B is wrong because 'show route table inet6.0' displays the IPv6 unicast route table, not IPv4 unicast routes. Option C is wrong because 'show route forwarding-table' displays the forwarding table (FIB), which contains the actual next-hop information used for packet forwarding, not the route table (RIB) that stores all learned routes. Option D is wrong because 'show route protocol bgp' filters the route table to show only routes learned via BGP, not the entire IPv4 unicast route table.

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57
MCQmedium

Refer to the exhibit. An engineer notices high error counts on the interface. Based on the output, what is the most likely cause?

A.The interface has a hardware fault.
B.The interface is experiencing excessive broadcasts.
C.The interface is operating in half-duplex mode.
D.The interface is connected to a device configured for half-duplex.
AnswerD

Correct; collisions on a full-duplex link indicate a duplex mismatch with the remote end.

Why this answer

The output shows high error counts on the interface, which is a classic symptom of a duplex mismatch. When one end of an Ethernet link operates in full-duplex and the other in half-duplex, collisions occur on the half-duplex side because it expects to wait for the carrier to be clear before transmitting, while the full-duplex side transmits at any time. This leads to frame check sequence (FCS) errors, alignment errors, and runts on the half-duplex interface.

Option D is correct because the local interface is likely full-duplex (default on modern Juniper devices), and the connected device is configured for half-duplex, causing the mismatch.

Exam trap

The trap here is that candidates often assume high error counts always indicate a hardware fault (Option A), but in JNCIA-JUNOS, the specific error types (e.g., collisions, late collisions) point to a duplex mismatch, not a physical layer failure.

How to eliminate wrong answers

Option A is wrong because a hardware fault typically manifests as a high rate of CRC errors or interface resets, not the specific pattern of errors seen in a duplex mismatch (e.g., excessive collisions and late collisions). Option B is wrong because excessive broadcasts cause high CPU utilization and broadcast storms, not physical-layer errors like FCS or alignment errors on the interface counters. Option C is wrong because if the local interface were operating in half-duplex, it would not be the cause of the high error counts; rather, the mismatch with a full-duplex peer would still be the issue, and the question states the engineer notices high error counts on the interface, implying the local interface is likely full-duplex.

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58
MCQmedium

Refer to the exhibit. Based on the output, what is the operational status of interface ge-0/0/0?

A.The interface is up but the link is down.
B.The interface has no IP address configured.
C.The interface is administratively down.
D.The interface is administratively up and the link is up.
AnswerD

Both Admin and Link are up.

Why this answer

Option D is correct because the output shows 'Physical link is Up' and 'Administratively Up', confirming that the interface is both enabled and receiving a carrier signal. In JUNOS, the 'show interfaces terse' command displays 'up' for the administrative status and 'up' for the link status when both conditions are met.

Exam trap

The trap here is that candidates often confuse the 'up/down' notation in 'show interfaces terse' with Cisco's 'show ip interface brief', where the first 'up' refers to the line protocol and the second to the administrative status, whereas JUNOS reverses the order (administrative first, then link).

How to eliminate wrong answers

Option A is wrong because the output explicitly states 'Physical link is Up', not down, so the link is operational. Option B is wrong because the interface does have an IP address configured (192.168.1.1/24 is shown in the output), and the absence of an IP address would not affect the operational status of the interface being up or down. Option C is wrong because the output shows 'Administratively Up', meaning the interface has not been disabled with the 'disable' command; if it were administratively down, the output would show 'Administratively Down'.

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59
MCQeasy

A network engineer wants to see all commands entered in the current session. Which operational mode command should they use?

A.history
B.show commands
C.show system history
D.show cli history
AnswerD

This command shows the history of CLI commands for the current session.

Why this answer

Option D is correct because 'show cli history' is the operational mode command in Junos that displays all commands entered during the current CLI session. This command retrieves the session-specific command history buffer, which is distinct from the system-wide history or shell history.

Exam trap

The trap here is that candidates familiar with Cisco IOS may mistakenly choose 'history' or 'show history' (which are valid Cisco commands) without realizing Junos uses the specific 'show cli history' syntax.

How to eliminate wrong answers

Option A is wrong because 'history' is not a valid Junos operational mode command; it is a Linux shell command that shows shell history, not Junos CLI session history. Option B is wrong because 'show commands' is not a valid Junos command; it is a generic phrase that might be confused with 'show configuration' or 'show system' but does not exist as a command. Option C is wrong because 'show system history' displays system log messages (syslog) or reboot history, not the CLI command history of the current session.

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60
MCQmedium

An engineer is configuring a firewall filter and wants to verify the syntax of the configuration before committing. Which command should be used?

A.validate
B.commit check
C.show | display inheritance
D.commit confirmed
AnswerB

Correctly validates the configuration syntax without committing.

Why this answer

The 'commit check' command validates the syntax and configuration semantics of the candidate configuration without activating it. This allows the engineer to verify that the firewall filter configuration is correct before committing, preventing potential service disruption from a faulty commit.

Exam trap

The trap here is that candidates familiar with Cisco IOS may confuse the Junos 'commit check' with the Cisco 'validate' command, but Junos uses 'commit check' for syntax verification and has no 'validate' command.

How to eliminate wrong answers

Option A is wrong because 'validate' is not a valid Junos CLI command; the correct command for syntax checking is 'commit check'. Option C is wrong because 'show | display inheritance' displays inherited configuration values, not syntax validation. Option D is wrong because 'commit confirmed' commits the configuration immediately and automatically rolls back if not confirmed within a timeout, which does not verify syntax before committing.

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61
Drag & Dropmedium

Arrange the steps to configure a static route in Junos OS in the correct order.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps
Order

Why this order

Static routes are configured under 'routing-options static' in Junos. After setting the route, you must commit and verify.

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62
MCQhard

Refer to the exhibit. An engineer runs the command shown. What does this output indicate?

A.The candidate configuration matches the committed configuration.
B.The candidate configuration has an IP address change.
C.The rollback 0 configuration is being displayed.
D.The interface ge-0/0/0 has been deleted.
AnswerB

The + and - lines indicate a change from 10.0.0.1 to 192.0.2.1.

Why this answer

The output shows the candidate configuration differs from the committed configuration, as indicated by the 'show | compare' command displaying a change under the [edit interfaces ge-0/0/0 unit 0 family inet] hierarchy. Specifically, it shows the address 192.168.1.1/24 being replaced with 192.168.1.2/24, which is an IP address change. This confirms option B is correct because the candidate configuration has an IP address change that has not yet been committed.

Exam trap

The trap here is that candidates often confuse 'show | compare' with 'show configuration | display set' or assume no output means no candidate changes exist, but in reality, 'show | compare' outputs only differences, and any output indicates a pending change that does not match the committed configuration.

How to eliminate wrong answers

Option A is wrong because the output shows a difference between the candidate and committed configurations (the IP address change), so they do not match; a matching configuration would produce no output from 'show | compare'. Option C is wrong because the command 'show | compare' compares the candidate configuration to the active (committed) configuration, not specifically to rollback 0; while rollback 0 is the most recent commit, the command compares to the current active configuration, and the output does not indicate a rollback operation. Option D is wrong because the output shows the interface ge-0/0/0 still exists with a unit and family inet configuration; only the IP address is changed, not the interface being deleted.

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63
MCQeasy

Refer to the exhibit. Which interface has an operational issue that prevents it from passing traffic?

A.ge-0/0/1
B.lo0
C.ge-0/0/2
D.ge-0/0/0
AnswerA

The link is down while administratively up, indicating a physical issue.

Why this answer

Interface ge-0/0/1 shows 'Link: DOWN' in the output, indicating a physical layer issue such as a disconnected cable, faulty transceiver, or administrative shutdown. A down link prevents any traffic from being forwarded over that interface, regardless of its protocol configuration.

Exam trap

The trap here is that candidates may focus on protocol state (e.g., 'Protocol: DOWN') or assume a loopback interface can pass transit traffic, but the key operational issue is the physical link state being down, which immediately blocks all traffic on that interface.

How to eliminate wrong answers

Option B (lo0) is wrong because the loopback interface is a virtual interface that is always up/up by default and does not have a physical link state; it is used for management and routing protocol stability, not for passing transit traffic. Option C (ge-0/0/2) is wrong because its output shows 'Link: Up' and 'Protocol: Up', meaning it is operationally capable of passing traffic. Option D (ge-0/0/0) is wrong because its output also shows 'Link: Up' and 'Protocol: Up', indicating no operational issue.

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64
MCQeasy

A junior admin wants to see all commands available in operational mode that start with 'show'. What keystrokes should they use?

A.show ? + Enter
B.show ?
C.show + ?
D.show <Tab>
AnswerB

Correctly lists all subcommands available under 'show'.

Why this answer

Option B is correct because in Junos operational mode, typing 'show ?' and pressing Enter (or just 'show ?' without Enter) displays all commands that start with 'show'. The question mark (?) is the context-sensitive help key that lists available completions for the current partial command. Pressing Enter after 'show ?' is optional but acceptable; the key behavior is the space followed by ?.

Exam trap

The trap here is that candidates familiar with Cisco IOS might confuse the Junos ? help with Cisco's ? or Tab behavior, where Tab in Cisco completes the command and ? lists options, but in Junos, Tab also completes but ? with a space lists all commands starting with the partial string, not just next keywords.

How to eliminate wrong answers

Option A is wrong because 'show ? + Enter' implies pressing Enter is required, but the ? alone triggers the help output without needing Enter; also, the space before ? is correct but the phrasing is misleading. Option C is wrong because 'show + ?' suggests typing 'show' then a plus sign, which is not a valid Junos keystroke sequence; the correct syntax is a space before the question mark. Option D is wrong because pressing Tab after 'show' performs command completion (auto-completes the command if unique), not listing all commands starting with 'show'; Tab is for completion, not for displaying available options.

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65
MCQmedium

An engineer wants to view system log messages as they are generated in real-time. Which command should they use?

A.start log messages
B.monitor log messages
C.request system log
D.show log messages
AnswerB

monitor log streams log messages to the terminal.

Why this answer

The 'monitor log messages' command in Junos OS provides a real-time view of system log messages as they are generated, similar to the 'tail -f' command on Unix systems. It streams new log entries to the terminal without requiring manual refresh, making it ideal for live monitoring of events.

Exam trap

The trap here is that candidates familiar with Cisco IOS may confuse 'show log' (which in Cisco shows a static log) with Junos 'show log messages', and incorrectly assume it provides real-time output, while 'monitor log messages' is the correct real-time equivalent.

How to eliminate wrong answers

Option A is wrong because 'start log messages' is not a valid Junos command; the correct command to begin logging is 'set system syslog' or similar configuration, not a real-time view. Option C is wrong because 'request system log' is used for operations like rotating or archiving log files, not for live viewing. Option D is wrong because 'show log messages' displays the contents of the /var/log/messages file at the time of execution, but does not provide real-time updates; it shows a static snapshot.

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66
Multi-Selecteasy

Which TWO commands can be used to view the current operational state of an interface? (Choose two.)

Select 2 answers
A.show interfaces extensive
B.show log
C.show configuration interfaces
D.show interfaces terse
E.show route
AnswersA, D

Shows detailed operational state.

Why this answer

The 'show interfaces extensive' command displays detailed operational state information, including current status, errors, and statistics. The 'show interfaces terse' command provides a concise operational view showing interface names, administrative status, link status, and protocol families. Both commands query the current operational state of interfaces from the Junos OS kernel.

Exam trap

The trap here is that candidates confuse 'show configuration interfaces' (which shows the intended configuration) with commands that show the actual operational state, leading them to select option C instead of the correct operational commands.

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67
Matchingmedium

Match each Junos CLI operational mode command to its function.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts
Matches

Displays brief interface status and configuration

Displays the routing table

Displays the current active configuration

Displays system log messages

Captures and displays live traffic on an interface

Why these pairings

These are common operational mode commands used for monitoring and troubleshooting in Junos.

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68
Matchingmedium

Match each Junos interface type to its typical use.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts
Matches

Out-of-band management interface

Gigabit Ethernet data interface

Loopback interface for router ID and management

Embedded management interface on some platforms

Generic routing encapsulation (GRE) tunnel

Why these pairings

These are common interface types in Junos.

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69
Multi-Selectmedium

Which TWO statements correctly describe the behavior of the Junos CLI operational mode?

Select 2 answers
A.Commands such as show and ping are available.
B.Command options are enclosed in curly braces { }.
C.Commands must be entered in full; abbreviation is not allowed.
D.You can commit configuration changes directly.
E.The CLI uses a hierarchical command structure.
AnswersA, E

Operational mode provides show and ping commands.

Why this answer

Option A is correct because Junos CLI operational mode provides commands for monitoring, troubleshooting, and verifying the device state, such as 'show' for displaying configuration and operational data, and 'ping' for network connectivity tests. These commands do not alter the active configuration, which is the defining characteristic of operational mode.

Exam trap

The trap here is that candidates familiar with Cisco IOS may assume curly braces indicate optional parameters (as in Cisco's syntax), but Junos uses square brackets for options and curly braces for configuration blocks, leading to confusion in identifying correct statements.

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70
Multi-Selecteasy

Which THREE statements about the Junos CLI help system are correct? (Choose three.)

Select 3 answers
A.Pressing <Tab> completes the current keyword if unique.
B.Pressing ? after a command shows available completions.
C.The 'help' command provides detailed documentation for specific topics.
D.Pressing <Ctrl+P> clears the command line.
E.Pressing ? at the beginning of a line shows all commands regardless of the current hierarchy level.
AnswersA, B, C

Correct; Tab auto-completes the partially typed keyword.

Why this answer

Option A is correct because the Junos CLI includes a tab-completion feature that, when you press the <Tab> key, automatically completes the current keyword if it is unique within the current hierarchy level. This speeds up command entry and reduces typing errors, a standard behavior in Junos.

Exam trap

The trap here is confusing Junos CLI help behavior with Cisco IOS, where pressing ? at the beginning of a line shows all commands regardless of mode, whereas Junos restricts completions to the current hierarchy level.

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71
MCQhard

During a maintenance window, a network engineer is about to commit changes but wants to ensure no active sessions are disrupted. Which command should they run first?

A.commit confirmed
B.commit check
C.commit synchronize
D.commit at
AnswerA

Commits with a timeout; if session is lost, automatically rolls back.

Why this answer

Option A is correct because the 'commit confirmed' command allows the engineer to apply changes with a default 10-minute rollback timer. If the commit is not confirmed within that window, Junos automatically reverts to the previous configuration, ensuring that any disruption caused by the changes is temporary and active sessions are not permanently affected.

Exam trap

The trap here is that candidates often confuse 'commit check' as a safe way to test changes, but it only validates syntax, not runtime behavior, and provides no automatic rollback to protect active sessions if the changes cause disruption.

How to eliminate wrong answers

Option B is wrong because 'commit check' only validates the syntax and semantic correctness of the candidate configuration without applying it; it does not provide any rollback mechanism to protect active sessions from disruption. Option C is wrong because 'commit synchronize' is used in a dual-RE (Routing Engine) chassis to apply the configuration to both REs simultaneously, but it does not offer a safety net like automatic rollback if the changes cause session drops. Option D is wrong because 'commit at' schedules the commit to occur at a specific time, but once committed, the changes are permanent unless manually reverted; it lacks the automatic rollback feature that protects active sessions during the maintenance window.

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72
MCQmedium

A network engineer is troubleshooting a BGP session that is not establishing. They want to see the BGP configuration details for peer 10.0.0.1. They type 'show configuration protocols bgp group external peer 10.0.0.1' but receive 'error: syntax error'. They are in operational mode. What is the most likely issue?

A.The peer IP 10.0.0.1 is not configured on the device.
B.The keyword 'peer' should be 'neighbor'.
C.The command should be 'show configuration protocols bgp group external | match 10.0.0.1'.
D.They need to enter configuration mode first.
AnswerB

In JunOS BGP configuration, the keyword 'neighbor' is used to refer to a BGP peer, not 'peer'.

Why this answer

In Junos OS, the correct keyword to reference a BGP peer in operational mode commands is 'neighbor', not 'peer'. The command 'show configuration protocols bgp group external neighbor 10.0.0.1' would display the configuration for that specific peer. Using 'peer' causes a syntax error because Junos does not recognize that keyword in this context.

Exam trap

The trap here is that candidates familiar with Cisco IOS, which uses 'neighbor' in configuration mode but 'peer' in some show commands, may incorrectly assume Junos uses 'peer' similarly, leading to a syntax error.

How to eliminate wrong answers

Option A is wrong because the syntax error occurs regardless of whether the peer IP is configured; the command itself is invalid due to the keyword 'peer'. Option C is wrong because while piping to 'match' could filter output, the primary issue is the incorrect keyword, and this workaround does not address the syntax error in the original command. Option D is wrong because 'show configuration' is a valid operational mode command; entering configuration mode is not required to view configuration details.

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73
MCQmedium

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?

A.Use the 'commit and-quit' command to apply changes.
B.Use the 'commit confirmed' command with a timeout.
C.Use the 'commit check' command before committing.
D.Use the 'rollback 0' command after committing.
AnswerB

Commit confirmed provides automatic rollback if not confirmed.

Why this answer

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.

Exam trap

The trap here is that candidates often confuse 'commit check' (syntax validation) with a rollback mechanism, or assume 'rollback 0' provides automatic reversion, when in fact it requires manual execution after the fact.

How to eliminate wrong answers

Option A is wrong because 'commit and-quit' is not a valid Junos command; the correct command is 'commit and-quit' to exit the configuration mode after committing, but it does not provide any automatic rollback capability. Option C is wrong because 'commit check' only validates the syntax and semantics of the candidate configuration without applying it; it does not allow reverting a change after it has been committed. Option D is wrong because 'rollback 0' reverts to the most recently committed configuration, but it must be issued manually after the change is already active, and it does not provide an automatic or timed rollback.

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74
MCQhard

A network operator is using the 'monitor traffic' command but wants to stop after capturing 100 packets. Which option should be added?

A.size 100
B.packets 100
C.limit 100
D.count 100
AnswerC

Correctly limits the packet capture to 100 packets.

Why this answer

The 'monitor traffic' command in Junos captures packets for analysis. To stop the capture after a specific number of packets, the correct option is 'limit 100', which instructs the command to terminate after processing 100 packets. This is a Junos-specific parameter for controlling the capture duration.

Exam trap

The trap here is that candidates may confuse Junos syntax with Cisco IOS, where 'packets' or 'count' are used in similar commands, leading them to select 'packets 100' or 'count 100' instead of the correct Junos-specific 'limit 100'.

How to eliminate wrong answers

Option A is wrong because 'size 100' is not a valid option for 'monitor traffic'; it would be used with other commands like 'monitor interface' to specify buffer size, not packet count. Option B is wrong because 'packets 100' is not a recognized parameter in Junos for this command; Junos uses 'limit' to specify the number of packets to capture. Option D is wrong because 'count 100' is not a valid option for 'monitor traffic'; 'count' is used in other contexts like firewall filters or show commands, not for packet capture termination.

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75
MCQhard

An engineer wants to see the differences between the active configuration and the candidate configuration. Which command should they use?

A.'show configuration | display set'
B.'show configuration | compare'
C.'run show configuration | compare'
D.'show | compare'
AnswerD

In configuration mode, this command shows diff between candidate and active.

Why this answer

Option D, 'show | compare', is correct because in the Junos CLI, the pipe (|) operator can be used to filter or modify the output of any operational mode command. When used with the 'compare' argument after 'show', it displays the differences between the active configuration and the candidate configuration. This is the standard syntax for comparing configurations in Junos.

Exam trap

The trap here is that candidates often confuse the 'show configuration' command with the 'show' command, and assume that 'compare' must be applied to 'configuration' specifically, when in fact the correct syntax is 'show | compare' without the 'configuration' keyword.

How to eliminate wrong answers

Option A is wrong because 'show configuration | display set' only converts the current configuration into 'set' commands format; it does not perform any comparison. Option B is wrong because 'show configuration | compare' is not valid syntax; the 'compare' argument must follow the pipe directly after 'show', not after 'configuration'. Option C is wrong because 'run show configuration | compare' is incorrect; 'run' is used to execute operational commands from configuration mode, but the correct command to compare configurations is simply 'show | compare' from operational mode.

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