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CCNA Junos Monitoring Questions

75 of 90 questions · Page 1/2 · Junos Monitoring topic · Answers revealed

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1

MCQeasy

Refer to the exhibit. Which interface has a physical layer connectivity problem?

A.ge-0/0/2

B.ge-0/0/0

C.ge-0/0/3

D.ge-0/0/1

AnswerD

ge-0/0/1 is administratively up but the link is down. This indicates a physical layer issue, such as a disconnected cable, faulty transceiver, or peer problem.

Why this answer

Interface ge-0/0/1 shows 'Physical link is Down' in the output, which directly indicates a physical layer connectivity problem. The 'Device present' field is also 'No', confirming that no transceiver or cable is detected, which is a Layer 1 issue.

Exam trap

The trap here is that candidates may focus on the 'Admin' status (up/down) rather than the 'Physical link' status, mistakenly assuming an administratively down interface is a physical layer problem, when in fact the physical layer issue is indicated by the link state being down regardless of administrative configuration.

How to eliminate wrong answers

Option A is wrong because ge-0/0/2 shows 'Physical link is Up' and 'Device present' is 'Yes', indicating no physical layer problem. Option B is wrong because ge-0/0/0 shows 'Physical link is Up' and 'Device present' is 'Yes', so the physical layer is functioning correctly. Option C is wrong because ge-0/0/3 shows 'Physical link is Up' and 'Device present' is 'Yes', meaning there is no physical layer connectivity issue.

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2

MCQhard

A network operator needs to upgrade the Junos OS on the backup RE (re1) of a dual-RE system. Which procedure ensures that only the backup RE is upgraded and rebooted without affecting the forwarding plane?

A.Use 'request system software add <image> re1' and then 'request system reboot re1'

B.Use 'request system software add <image> both' and then 'request system reboot both'

C.Use 'request system software add <image> re0' and then 'request system reboot re0'

D.Copy the image to both REs and reboot the backup RE with 'request system reboot slice 1'

AnswerA

This sequence adds the image to re1 only and reboots only that RE. The primary RE continues running, so forwarding is unaffected.

Why this answer

Option A is correct because the 'request system software add <image> re1' command installs the Junos OS image only on the backup Routing Engine (RE1), and the subsequent 'request system reboot re1' reboots only that RE. In a dual-RE system, this procedure isolates the upgrade to the backup RE, ensuring the forwarding plane remains active on the primary RE (RE0) and no traffic disruption occurs.

Exam trap

The trap here is that candidates may confuse the 'both' option with a safe upgrade method, not realizing it reboots both REs simultaneously and disrupts traffic, or they may incorrectly assume that copying the image manually and using a non-existent 'slice' command is a valid procedure.

How to eliminate wrong answers

Option B is wrong because 'request system software add <image> both' and 'request system reboot both' upgrade and reboot both REs simultaneously, which would disrupt the forwarding plane by causing a full system outage. Option C is wrong because 'request system software add <image> re0' and 'request system reboot re0' target the primary RE, which would interrupt the forwarding plane and potentially cause a traffic loss. Option D is wrong because 'request system reboot slice 1' is not a valid Junos command for rebooting a specific RE; the correct syntax uses 're0' or 're1' to specify the Routing Engine, and copying the image to both REs without using the proper 'request system software add' command does not ensure a controlled upgrade.

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3

MCQeasy

A network administrator is troubleshooting high latency on a link. Which command provides real-time interface statistics?

A.show interfaces extensive

B.monitor interface traffic

C.show interfaces terse

D.show log messages

AnswerB

Provides real-time bandwidth utilization and packet counts.

Why this answer

Option B is correct because 'monitor interface traffic' shows live traffic statistics. Option A shows a static brief summary. Option C shows detailed but static output.

Option D shows historical log messages.

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4

MCQeasy

A network administrator wants to see the current CPU load average over the last 1, 5, and 15 minutes on a Juniper device. Which command displays this information?

A.show chassis routing-engine

B.show system uptime

C.show system processes

D.show system statistics

AnswerB

The 'show system uptime' command displays system load averages for 1, 5, and 15 minutes. This is the standard way to monitor CPU load averages.

Why this answer

The 'show system uptime' command displays the system's uptime along with the load averages for the last 1, 5, and 15 minutes. This is the standard Junos command for viewing CPU load averages, which are calculated based on the number of processes in the run queue over those time intervals.

Exam trap

The trap here is that candidates often confuse 'show chassis routing-engine' (which shows current CPU utilization) with the load average command, not realizing that load averages are a separate time-weighted metric displayed by 'show system uptime'.

How to eliminate wrong answers

Option A is wrong because 'show chassis routing-engine' displays the status and resource utilization of the Routing Engine (including CPU and memory), but it does not show the load average over 1, 5, and 15 minutes; it shows current CPU utilization percentage. Option C is wrong because 'show system processes' lists all running processes with their PID, memory, and CPU usage, but it does not aggregate the load average over time intervals. Option D is wrong because 'show system statistics' displays various system-wide counters and statistics (e.g., packet counts, memory usage), but it does not include CPU load averages.

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5

MCQeasy

A network engineer notices that a device is not sending SNMP traps to the NMS. Which operational command should be used to verify SNMP configuration?

A.show system uptime

B.show route

C.show snmp

D.show interfaces terse

AnswerC

Displays SNMP configuration and trap settings.

Why this answer

The 'show snmp' command in Junos displays the current SNMP configuration, including community strings, trap destinations, and enabled trap groups. Since the issue is that the device is not sending SNMP traps, this command allows the engineer to verify that trap destinations are correctly configured and that the appropriate trap groups are enabled. Other commands like 'show system uptime' or 'show route' do not provide any SNMP-specific configuration details.

Exam trap

The trap here is that candidates often confuse 'show snmp' with 'show snmp statistics' or 'show snmp mib walk', but the question specifically asks for verifying configuration, not statistics or MIB data, making 'show snmp' the correct operational command.

How to eliminate wrong answers

Option A is wrong because 'show system uptime' displays the system uptime and load averages, not SNMP configuration or trap settings. Option B is wrong because 'show route' displays the routing table and is used for verifying network reachability, not SNMP trap configuration. Option D is wrong because 'show interfaces terse' shows a summary of interface status and configuration, which is unrelated to SNMP trap settings.

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6

Multi-Selecthard

Which THREE statements about the 'request system snapshot' command are true? (Choose three.)

Select 3 answers

A.It creates a recovery media for the device.

B.It compresses the backup to save space.

C.It backs up the current Junos OS and configuration to alternate media.

D.It copies the active partition to the alternate partition on the same media.

E.It can be used to restore the software and configuration in case of failure.

AnswersA, C, E

Correct: Snapshots create bootable recovery media.

Why this answer

Option A is correct because the 'request system snapshot' command creates a bootable recovery media (e.g., USB or compact flash) that contains a copy of the current Junos OS and configuration. This allows the device to boot from that media in case of a system failure, effectively serving as a recovery tool.

Exam trap

The trap here is that candidates confuse 'request system snapshot' with 'request system snapshot partition', which copies the active partition to the alternate partition on the same media, not to external media.

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7

Multi-Selecthard

Which two commands can be used to capture the current interface statistics and save them for later analysis? (Choose two.)

Select 2 answers

A.file archive interface-statistics

B.request system statistics interface

C.show interfaces statistics | save /var/log/iface_stats.txt

D.show interfaces extensive | save /var/log/iface_extensive.txt

E.monitor interface traffic | save /var/log/iface_traffic.txt

AnswersC, D

Saves interface statistics output to a file.

Why this answer

Option C is correct because the 'show interfaces statistics' command displays current interface counters (e.g., input/output packets, errors, discards) and piping the output to '| save /var/log/iface_stats.txt' writes the snapshot to a file for later analysis. This allows you to capture a point-in-time record of interface statistics without ongoing monitoring.

Exam trap

The trap here is that candidates may confuse 'monitor interface traffic' (a real-time, continuous command) with 'show interfaces statistics' (a static snapshot), or assume that 'request system statistics interface' is a valid Junos command when it is not, leading them to select option B or E incorrectly.

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8

MCQhard

You are the network administrator for a large enterprise with a Juniper MX480 router running Junos 18.2R3. The router has two Routing Engines (RE0 and RE1) in a graceful Routing Engine switchover (GRES) configuration. During a scheduled maintenance window, you need to upgrade the Junos OS to a newer version while minimizing traffic loss. The upgrade process requires a reboot of both REs. You have staged the software on both REs. Which sequence of commands should you use to perform the upgrade with minimal disruption?

A.On both REs: request system software add <image>; then request system reboot both REs simultaneously.

B.On RE0: request system software add <image> re0; on RE1: request system software add <image> re1; then request system reboot both.

C.On RE0 (primary): request system software add <image> re0; request system reboot re0. After reboot, on RE1: request system software add <image> re1; request system reboot re1.

D.On RE1 (backup): request system software add <image> re1; request system reboot re1. After reboot, request chassis routing-engine master switch. On RE0 (now backup): request system software add <image> re0; request system reboot re0.

AnswerD

Correct: Follows best practice for minimal disruption.

Why this answer

Option D is correct because it performs a hitless upgrade by first upgrading and rebooting the backup RE (RE1), then performing a graceful mastership switch using 'request chassis routing-engine master switch', and finally upgrading and rebooting the former primary (now backup) RE0. This sequence ensures that during each RE reboot, the other RE remains active and continues forwarding traffic, leveraging GRES to maintain state and minimize packet loss.

Exam trap

The trap here is that candidates assume 'request system reboot both' or rebooting the primary first is acceptable, not realizing that GRES requires a sequential upgrade with a manual mastership switch to avoid a full outage.

How to eliminate wrong answers

Option A is wrong because rebooting both REs simultaneously would cause a complete loss of routing and forwarding capability, defeating the purpose of GRES and causing significant traffic disruption. Option B is wrong because issuing 'request system reboot both' still reboots both REs at the same time, even though the software is staged individually, resulting in the same outage as Option A. Option C is wrong because rebooting the primary RE (RE0) first without first switching mastership to the backup causes the backup to take over abruptly, but more critically, the backup RE1 still has the old software and must be rebooted later, leading to a second outage window; the sequence does not leverage GRES to minimize disruption.

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9

Drag & Dropmedium

Arrange the steps to configure a DHCP server on a Junos router.

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

Steps

Order

Why this order

DHCP server configuration involves defining pools, options, and exclusions.

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10

Multi-Selectmedium

Which THREE statements are true about the commit operation on Junos?

Select 3 answers

A.The commit operation validates the configuration before applying.

B.The commit operation can be confirmed with a time delay.

C.The candidate configuration is activated immediately upon commit.

D.The commit operation always requires a reboot.

E.A commit check can be performed without committing.

AnswersA, B, C

Junos performs validation checks (syntax, semantics) before applying the commit. If validation fails, the commit is rejected.

Why this answer

Option A is correct because the `commit` operation in Junos first validates the candidate configuration for syntax and semantic errors before applying it. If validation fails, the commit is aborted and the candidate configuration remains unchanged, ensuring operational stability.

Exam trap

The trap here is that candidates may think a commit always requires a reboot (Option D) due to experience with other vendors, or they may incorrectly believe that a commit check cannot be performed without committing (Option E), when in fact `commit check` is a standard Junos command that validates without applying.

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11

MCQhard

After a software upgrade, BGP sessions are not establishing. The engineer runs 'show bgp summary' and sees that all sessions are in Idle state. What is the most likely cause?

A.The BGP group configuration is missing

B.The interface is administratively down

C.The router has a full BGP table

D.The firewall filter is blocking ICMP

AnswerA

Without proper configuration, BGP cannot start.

Why this answer

The Idle state in BGP indicates that the session has not started the connection process, often because the BGP configuration is incomplete or missing. If the BGP group configuration is missing, the router has no peers to initiate sessions with, so all sessions remain in Idle. This is the most likely cause when all sessions are in Idle after a software upgrade, as configuration elements may be lost or not applied.

Exam trap

The trap here is that candidates often associate Idle state with connectivity issues like interface down or firewall filters, but Idle specifically indicates the BGP process has not been initiated due to missing or incomplete configuration, not a network problem.

How to eliminate wrong answers

Option B is wrong because an administratively down interface would cause the BGP session to be stuck in Active or Connect state, not Idle, as the router would still attempt to establish a TCP connection. Option C is wrong because a full BGP table does not prevent session establishment; it may cause memory or processing issues but the session state would be Established or possibly Idle due to resource exhaustion, not universally Idle. Option D is wrong because a firewall filter blocking ICMP would not affect BGP session establishment, as BGP uses TCP port 179, not ICMP; blocking ICMP could impact path MTU discovery but not the TCP handshake itself.

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12

MCQeasy

Based on the exhibit, which protocol is enabled on interface ge-0/0/0.0?

A.IS-IS

C.MPLS

AnswerC

Correct: MPLS is listed under Protocols.

Why this answer

The exhibit shows that interface ge-0/0/0.0 has the 'family mpls' statement configured under it, which enables MPLS on that interface. MPLS is explicitly enabled at the protocol family level, allowing the interface to participate in MPLS label switching.

Exam trap

The trap here is that candidates often confuse 'family mpls' with enabling a routing protocol like OSPF or IS-IS, not realizing that MPLS is a separate protocol family configured directly on the interface, not under the routing protocol hierarchy.

How to eliminate wrong answers

Option A is wrong because IS-IS is a routing protocol that would be enabled under the 'protocols isis' hierarchy, not by configuring 'family mpls' on the interface. Option B is wrong because BGP is a routing protocol configured under 'protocols bgp' and requires an address family (e.g., inet unicast) to be enabled, not 'family mpls'. Option D is wrong because OSPF is enabled under 'protocols ospf' and uses 'interface' statements within that hierarchy, not by setting 'family mpls' on the interface.

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13

MCQeasy

A Juniper device is running out of disk space on the /var partition. Which command can be used to check disk usage?

A.show system storage

B.show system disk-space

C.show system memory

D.show system resource

AnswerA

Displays filesystem usage including /var.

Why this answer

The correct command to check disk usage on a Juniper device is 'show system storage'. This command displays detailed information about disk partitions, including total, used, and available space, as well as the percentage of usage for each mounted filesystem, such as /var. It is the standard operational mode command for monitoring storage utilization in Junos OS.

Exam trap

The trap here is that candidates familiar with other operating systems might expect a command like 'show system disk-space' or confuse memory with storage, but Junos uses the specific phrase 'storage' for disk usage monitoring.

How to eliminate wrong answers

Option B is wrong because 'show system disk-space' is not a valid Junos command; the correct command uses 'storage' not 'disk-space'. Option C is wrong because 'show system memory' displays RAM and memory utilization, not disk storage. Option D is wrong because 'show system resource' shows system resource usage like CPU and memory, but does not provide disk partition or filesystem usage details.

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14

MCQhard

Refer to the exhibit. Based on the log output, what is the most likely issue with interface ge-0/0/1?

A.Interface is experiencing flapping

B.Interface is up and stable

C.Interface is administratively down

D.Interface is configured incorrectly

AnswerA

Repeated up/down events indicate flapping.

Why this answer

The log output shows repeated 'link UP' and 'link DOWN' events for interface ge-0/0/1 within a short time window, which is the classic symptom of interface flapping. Flapping typically occurs due to physical layer issues such as faulty cables, damaged transceivers, or marginal signal integrity, causing the interface to continuously transition between up and down states.

Exam trap

The trap here is that candidates may assume any interface issue is configuration-related (Option D) or that a single 'link UP' message means the interface is stable (Option B), but the repeated pattern of alternating UP/DOWN events is the definitive indicator of flapping.

How to eliminate wrong answers

Option B is wrong because the log clearly shows the interface is not stable; it is oscillating between up and down states, which contradicts the definition of a stable interface. Option C is wrong because an administratively down interface would show a 'administratively down' status in the log, not repeated link transitions; the interface is actively trying to come up. Option D is wrong because while configuration errors can cause operational issues, the specific pattern of rapid link state changes points to a physical or Layer 1 problem, not a configuration mistake like incorrect VLAN or IP settings.

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15

Drag & Dropmedium

Arrange the steps to configure OSPF on a Junos router 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

OSPF requires a router ID and interfaces assigned to areas. Verification shows neighbor relationships.

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16

MCQhard

An administrator observes that the router's CPU utilization is consistently high. Which command helps identify which process is consuming the most CPU?

A.show log messages

B.show system resource

C.show chassis routing-engine

D.show system processes extensive

AnswerD

Shows CPU usage per process.

Why this answer

Option D, 'show system processes extensive', is correct because it displays detailed CPU utilization statistics for each running process on a Junos device, including the percentage of CPU time consumed. This allows the administrator to identify which specific process (e.g., routing protocol daemon, SNMP, or management process) is causing the high CPU load, enabling targeted troubleshooting.

Exam trap

The trap here is that candidates often confuse 'show chassis routing-engine' (which shows aggregate CPU load) with process-level CPU breakdown, leading them to choose option C, but only 'show system processes extensive' provides the per-process detail needed to pinpoint the culprit.

How to eliminate wrong answers

Option A is wrong because 'show log messages' displays system log entries (syslog messages) and does not provide real-time CPU utilization per process; it is used for reviewing events and errors, not for process-level CPU monitoring. Option B is wrong because 'show system resource' shows overall system resource usage (memory, CPU, and storage) but does not break down CPU usage by individual process; it gives a high-level summary, not per-process granularity. Option C is wrong because 'show chassis routing-engine' displays the status and resource utilization of the Routing Engine (RE), including CPU load average, but it does not list individual processes; it shows aggregate RE health, not process-specific CPU consumption.

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17

MCQeasy

An engineer needs to check the current system uptime on a Juniper device running Junos OS. Which command should they use?

A.show system status

B.show system health

C.show system resources

D.show system uptime

AnswerD

Correct command to view system uptime.

Why this answer

The correct command to check current system uptime on a Juniper device running Junos OS is 'show system uptime'. This command displays the time since the system was last booted, as well as the current time and the time since the routing protocol process (rpd) started. It is the standard operational command for this specific metric.

Exam trap

The trap here is that candidates may confuse 'show system uptime' with similar-sounding commands from other vendors (like Cisco's 'show version' or 'show system status'), leading them to select a non-existent or incorrect Junos command.

How to eliminate wrong answers

Option A is wrong because 'show system status' is not a valid Junos command; the correct command for general system status information is 'show system information'. Option B is wrong because 'show system health' is not a valid Junos command; the correct command for hardware health monitoring is 'show chassis hardware' or 'show system health-monitor' (in newer releases). Option C is wrong because 'show system resources' displays CPU, memory, and filesystem utilization, not system uptime.

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18

MCQmedium

An administrator wants to verify that BGP neighbors are established. Which command provides a summary of all BGP peer sessions?

A.show bgp neighbor

B.show bgp summary

C.show interfaces terse

D.show route protocol bgp

AnswerB

Provides a summary of BGP peer sessions.

Why this answer

The 'show bgp summary' command is correct because it provides a concise, one-line-per-peer overview of all BGP sessions, including the peer IP address, AS number, state (e.g., Established), and counters for prefixes received. This is the standard command in Junos for quickly verifying that all BGP neighbors are in the Established state without the detailed per-neighbor output.

Exam trap

The trap here is that candidates familiar with Cisco IOS might expect 'show ip bgp summary' but mistakenly choose 'show bgp neighbor' because they confuse the detailed neighbor output with a summary view, or they overlook that Junos uses 'show bgp summary' for the aggregated peer list.

How to eliminate wrong answers

Option A is wrong because 'show bgp neighbor' displays detailed per-neighbor information (including timers, capabilities, and NLRI details) for each BGP peer, not a summary table. Option C is wrong because 'show interfaces terse' lists interface status and configuration, not BGP peer session information. Option D is wrong because 'show route protocol bgp' displays the routing table entries learned via BGP, not the status of BGP peer sessions.

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19

MCQmedium

After a configuration change, a router is not behaving as expected. The administrator wants to rollback to the previous configuration. Which command accomplishes this?

A.rollback 0

B.commit check

C.rollback 1

D.load override current

AnswerC

Reverts to the previous committed configuration.

Why this answer

Option C is correct because the 'rollback 1' command reverts the active configuration to the most recent committed configuration (the one before the latest commit). In JUNOS, the rollback command uses a numeric index where 0 is the current active configuration, 1 is the previous committed configuration, and higher numbers go further back. This allows the administrator to undo an unwanted configuration change without manually editing the configuration.

Exam trap

The trap here is that candidates familiar with Cisco IOS might think 'rollback 0' undoes the last change, but in JUNOS, rollback 0 refers to the current active configuration, not the previous one.

How to eliminate wrong answers

Option A is wrong because 'rollback 0' reverts to the current active configuration, which is effectively a no-op and does not undo any changes. Option B is wrong because 'commit check' only validates the syntax and semantics of the candidate configuration without committing it; it does not roll back to a previous configuration. Option D is wrong because 'load override current' is not a valid JUNOS command; the correct command to replace the candidate configuration with the current active configuration is 'load override terminal' or 'load override <filename>', but this does not roll back to a previous committed configuration.

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20

Matchingmedium

Match each Junos operational command for monitoring to its output.

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

Concepts

Matches

Lists interfaces with status and IP addresses

Displays ARP table

Displays system log messages

Displays IPv4 unicast routing table

Continuously displays interface statistics

Why these pairings

These commands help monitor and troubleshoot the system.

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21

MCQeasy

You are managing a Juniper MX240 router at a small ISP. The router has been operating normally for months. This morning, a customer reports intermittent packet loss on their connection, which is served by interface ge-0/0/2. You SSH into the router and run 'show interfaces ge-0/0/2 extensive'. The output shows input errors increasing rapidly, including CRC errors and frame errors. The interface is up/up. You also notice that the interface statistics show a high number of carrier transitions. The cable connecting the router to the customer's CPE was recently replaced by the customer's technician. What is the most likely cause of the errors and the correct action to resolve the issue?

A.Clear the MAC address table on the router to fix possible MAC flapping issues.

B.Administer a 'shutdown' and 'no shutdown' on the interface to reset the line protocol.

C.Replace the cable with a known good one because CRC and frame errors indicate a physical layer problem such as a damaged cable or loose connector.

D.Change the interface speed and duplex settings to auto-negotiate because the errors are due to a mismatch between the router and CPE.

AnswerC

CRC/frame errors and carrier transitions point to physical layer issues; the recent cable change makes this likely.

Why this answer

CRC and frame errors increasing rapidly, combined with a high number of carrier transitions, are classic symptoms of a physical-layer issue. Since the cable was recently replaced by the customer's technician, the most likely cause is a faulty cable or a loose connector. Replacing the cable with a known good one directly addresses the physical layer problem, which is the root cause of these errors.

Exam trap

The trap here is that candidates may confuse CRC/frame errors with a speed/duplex mismatch (Option D) or think a simple interface reset (Option B) will fix the problem, when the rapid increase in carrier transitions and the recent cable replacement clearly indicate a physical cabling fault.

How to eliminate wrong answers

Option A is wrong because MAC address table clearing addresses MAC flapping, which is a Layer 2 issue unrelated to CRC/frame errors or carrier transitions. Option B is wrong because administratively resetting the interface (shutdown/no shutdown) would only temporarily clear counters and restart the line protocol, but it would not fix the underlying physical-layer problem causing the errors. Option D is wrong because while speed/duplex mismatch can cause errors, the presence of carrier transitions and the recent cable replacement strongly point to a physical cabling issue, not a negotiation mismatch; auto-negotiation is already the default on modern Juniper interfaces and would not resolve a faulty cable.

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22

MCQeasy

To monitor interface traffic in real-time, which operational command is most appropriate?

A.show interface traffic

B.request system reboot

C.show log

D.monitor interface

AnswerD

Provides real-time interface traffic updates.

Why this answer

The 'monitor interface' command in Junos provides real-time, continuous display of interface statistics and traffic counters, updating every second by default. This is the correct operational command for live traffic monitoring, as it refreshes the output dynamically without requiring manual re-entry.

Exam trap

The trap here is that candidates familiar with Cisco IOS may mistakenly expect a 'show interface traffic' command (similar to 'show interfaces' with counters) and overlook the Junos-specific 'monitor interface' command for real-time updates.

How to eliminate wrong answers

Option A is wrong because 'show interface traffic' is not a valid Junos command; the correct static display command is 'show interfaces traffic' which shows a snapshot, not real-time updates. Option B is wrong because 'request system reboot' is used to reboot the device, not to monitor traffic, and would disrupt operations. Option C is wrong because 'show log' displays system log messages from files like messages or interactive-commands, which are not designed for real-time interface traffic monitoring and lack live counter updates.

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23

MCQhard

A Juniper SRX300 firewall is deployed at a branch office. The firewall's disk space on /var is critically low, causing logs to stop writing and system performance degradation. You need to free up space quickly without deleting logs (they are required for compliance). Which action should you take?

A.Increase the /var partition size using LVM.

B.Enable log rotation with smaller retention to prevent future growth.

C.Move logs to an NFS mount using 'file copy' and delete local copies.

D.Compress old log files using 'request system storage compress'.

AnswerD

Compresses logs to reclaim space without deletion.

Why this answer

Option D is correct because the 'request system storage compress' command compresses inactive log files on the /var partition, freeing up disk space without deleting any logs. This preserves the logs for compliance requirements while immediately alleviating the low disk space condition. The command targets files that are not currently being written to, such as rotated or archived logs, and compresses them using gzip.

Exam trap

The trap here is that candidates may confuse 'compress' with 'delete' or think that log rotation alone solves the immediate space issue, but the question explicitly requires freeing space quickly without deleting logs, making compression the only viable option.

How to eliminate wrong answers

Option A is wrong because Juniper SRX300 devices do not use LVM (Logical Volume Manager); they use a fixed partition layout that cannot be dynamically resized without reinstalling the Junos OS. Option B is wrong because enabling log rotation with smaller retention prevents future growth but does not free up space already consumed; the question requires an immediate action to address the critically low disk space. Option C is wrong because 'file copy' is a shell command that copies files but does not automatically delete the source; manually moving logs to an NFS mount and deleting local copies is a multi-step process that risks data loss or incomplete cleanup, and Junos does not have a built-in 'move and delete' command for this purpose.

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24

Multi-Selectmedium

Which TWO statements are true about the 'show interfaces ge-0/0/0 extensive' command output?

Select 2 answers

A.It displays a detailed count of errors

B.It includes only layer 1 information

C.It provides traffic statistics

D.It shows the interface configuration

E.It indicates the administrative status

AnswersA, C

Extensive includes error counters.

Why this answer

The 'show interfaces ge-0/0/0 extensive' command in Junos OS provides a comprehensive view of the interface, including detailed error counters (e.g., CRC errors, frame errors, giants, runts) and traffic statistics (e.g., input/output bytes, packets, and rates). Option A is correct because the extensive output explicitly lists a detailed count of errors per interface, which is not available in the standard 'show interfaces' output. Option C is correct because traffic statistics such as unicast, multicast, and broadcast packets are included in the extensive output.

Exam trap

The trap here is that candidates often assume 'extensive' only adds more Layer 1 details, but it actually includes Layer 2 and Layer 3 operational data, and they may also confuse operational output with configuration commands.

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25

MCQhard

A network administrator is troubleshooting a routing issue and wants to view the routing table for a specific routing instance called 'VPN-A'. Which command should they use?

A.show routing-table VPN-A

B.show route table VPN-A

C.show route instance VPN-A

D.show routing instance VPN-A route

AnswerB

Shows routes for the specified routing instance.

Why this answer

The correct command to view the routing table for a specific routing instance in Junos is 'show route table VPN-A'. This command displays the routes associated with the routing instance named 'VPN-A', which is essential for troubleshooting routing issues within that instance. The 'show route' command is the standard way to view routing tables, and specifying the 'table' keyword followed by the instance name targets the correct routing table.

Exam trap

The trap here is that candidates familiar with Cisco IOS might expect 'show ip route vrf VPN-A' and incorrectly apply similar syntax like 'show routing-table VPN-A' or 'show route instance VPN-A', not realizing Junos uses 'show route table <instance-name>' for the same purpose.

How to eliminate wrong answers

Option A is wrong because 'show routing-table VPN-A' is not a valid Junos command; the correct syntax uses 'show route table' not 'show routing-table'. Option C is wrong because 'show route instance VPN-A' is not a valid command; 'show route instance' does not exist, and the correct command to view routing instance details is 'show routing instance VPN-A', which shows configuration and status but not the routing table. Option D is wrong because 'show routing instance VPN-A route' is syntactically incorrect; the proper command to view the routing table for an instance is 'show route table VPN-A', not a combination of 'routing instance' and 'route'.

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26

Multi-Selecteasy

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

Select 2 answers

A.monitor interface

B.monitor traffic

C.show log

D.request system reboot

E.show system storage

AnswersA, B

Provides real-time interface statistics.

Why this answer

The `monitor interface` command provides a real-time, continuously updating view of interface statistics, including traffic counters, errors, and operational status. The `monitor traffic` command captures and displays live packet headers or full packets on an interface, useful for real-time traffic analysis. Both commands are designed for live monitoring, unlike static `show` commands or administrative actions.

Exam trap

The trap here is confusing static `show` commands (like `show interfaces`) with real-time `monitor` commands, or assuming that any command displaying data is real-time, when only `monitor` commands provide live, updating output.

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27

MCQeasy

A network engineer needs to check the system's disk space usage. Which command should be used?

A.show system storage

B.show configuration

C.show version

D.show system uptime

AnswerA

Displays disk space usage.

Why this answer

The 'show system storage' command displays disk space usage on Junos devices, including total, used, and available space for each mounted filesystem. This is the correct command for monitoring storage utilization, as it directly reports on the /, /config, and /var partitions critical for system operation.

Exam trap

The trap here is that candidates might confuse 'show system storage' with 'show system uptime' or 'show version' because they all start with 'show system', but only 'show system storage' provides disk space information.

How to eliminate wrong answers

Option B is wrong because 'show configuration' displays the active configuration, not disk space usage. Option C is wrong because 'show version' shows software version and hardware model information, not storage details. Option D is wrong because 'show system uptime' displays how long the device has been running and load averages, not disk space.

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28

Multi-Selectmedium

Which TWO commands can be used to monitor system log messages in real-time?

Select 2 answers

A.show log messages | last 100

B.show system log messages

C.show configuration system syslog

D.monitor start interactive-commands

E.monitor start messages

AnswersD, E

The 'monitor start interactive-commands' command displays real-time output of user commands logged to the interactive-commands log file. It is another real-time monitoring option.

Why this answer

Option D is correct because the 'monitor start interactive-commands' command in Junos OS enables real-time monitoring of interactive commands executed on the device, displaying them as they occur. Option E is correct because 'monitor start messages' streams the contents of the /var/log/messages file in real-time, allowing you to see new syslog entries as they are generated. Both commands use the 'monitor start' family, which is specifically designed for real-time log monitoring, unlike 'show log' which only displays historical data.

Exam trap

The trap here is that candidates confuse static 'show log' commands (which display historical log data) with dynamic 'monitor start' commands (which provide real-time streaming), and may also mistakenly think 'show system log messages' is a valid command when it is not.

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29

MCQeasy

An administrator notices that the routing table is not updating as expected. Which command should be used to verify the routing table contents?

A.show log

B.show route

C.show system storage

D.show interfaces

AnswerB

Displays the routing table.

Why this answer

The 'show route' command displays the routing table, which contains all active routes learned via static configuration, direct interfaces, or dynamic routing protocols such as OSPF, IS-IS, BGP, and RIP. If the routing table is not updating as expected, this command allows the administrator to verify the current routes, their next hops, and protocol sources to identify missing or incorrect entries.

Exam trap

The trap here is that candidates may confuse 'show route' with 'show interfaces' or 'show log', thinking that interface status or log messages would directly reveal routing table updates, when in fact only 'show route' provides the definitive view of the routing table contents.

How to eliminate wrong answers

Option A is wrong because 'show log' displays system log messages (e.g., from syslog or traceoptions), not the routing table contents; it is used for troubleshooting events, not for viewing route entries. Option C is wrong because 'show system storage' reports disk usage and file system space, which is unrelated to routing table updates. Option D is wrong because 'show interfaces' displays interface status, statistics, and configuration, but does not show the routing table; it is used for verifying link-level connectivity, not route propagation.

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30

MCQhard

You are a network administrator for a large enterprise. The Juniper EX4300 switch that serves as the distribution layer for the finance department is experiencing high CPU utilization. Users are complaining of slow network performance. You have accessed the switch via console and notice that the CPU load is consistently above 90%. You need to identify the process causing the high CPU usage. Which command should you use?

A.'show task summary' to see kernel task CPU usage.

B.'show system processes' to list all processes and their CPU usage.

C.'show system resources' to check memory and CPU.

D.'show system statistics' to view overall system stats.

AnswerB

Displays CPU and memory usage per process to identify the culprit.

Why this answer

The 'show system processes' command displays a list of all running processes along with their CPU and memory usage, allowing you to identify which process is consuming excessive CPU resources. This is the direct method to pinpoint the offending process on a Juniper EX4300 switch running Junos OS.

Exam trap

The trap here is that candidates confuse 'show system resources' (which shows aggregate CPU/memory) with the per-process breakdown needed to identify the specific process, leading them to choose option C instead of B.

How to eliminate wrong answers

Option A is wrong because 'show task summary' displays kernel task statistics (such as task name, CPU time, and state) but does not provide per-process CPU usage percentages needed to identify the specific process causing high CPU. Option C is wrong because 'show system resources' shows overall CPU and memory utilization but does not break down usage by individual processes. Option D is wrong because 'show system statistics' displays cumulative system counters (like packets, errors, and drops) rather than per-process CPU consumption.

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31

MCQmedium

An administrator needs to verify the current time and time zone configured on the Juniper device. Which command should they use?

A.show system uptime

B.show system clock

C.show system information

D.show system date

AnswerB

Displays current system date and time.

Why this answer

The correct command is 'show system clock' because it displays the current system time and time zone configured on the Juniper device. This command is specifically designed to show the local time, time zone offset, and whether daylight saving time is active, making it the precise tool for verifying time and time zone settings.

Exam trap

The trap here is that candidates confuse 'show system uptime' with time display, but uptime only shows elapsed time since boot, not the current clock time or time zone.

How to eliminate wrong answers

Option A is wrong because 'show system uptime' displays how long the device has been running since last reboot, along with load averages and users, but does not show the configured time zone. Option C is wrong because 'show system information' shows hardware model, serial number, software version, and other system details, but not the current time or time zone. Option D is wrong because 'show system date' is not a valid Junos command; the correct command for date/time display is 'show system clock'.

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32

Multi-Selecteasy

An engineer needs to check for packet errors on an interface. Which two commands provide error counter information? (Choose two.)

Select 2 answers

A.show interfaces diagnostics

B.show interface errors

C.show interfaces extensive

D.show interfaces errors

E.show interfaces terse

AnswersC, D

'show interfaces extensive' includes detailed error counters among other information.

Why this answer

Option B, 'show interfaces errors', provides a concise view of error counters per interface. Option C, 'show interfaces extensive', includes detailed error statistics. Option A shows a brief summary without errors.

Option D is invalid syntax (singular 'interface'). Option E shows optical diagnostics, not packet errors.

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33

MCQmedium

A network administrator is troubleshooting high CPU usage on a Juniper router. Which command helps identify which process is consuming the most CPU?

A.show log messages

B.show system memory

C.show system processes extensive

D.show interfaces

AnswerC

Displays detailed process CPU usage.

Why this answer

The 'show system processes extensive' command displays detailed information about all running processes, including CPU utilization, memory usage, and process IDs. This allows the administrator to identify which process (e.g., routing protocol daemon, management daemon) is consuming the most CPU cycles, directly addressing the troubleshooting need.

Exam trap

The trap here is that candidates often confuse 'show system processes extensive' with 'show system memory' or 'show log messages', mistakenly thinking memory or log analysis will reveal CPU hogs, when only the process list provides per-process CPU metrics.

How to eliminate wrong answers

Option A is wrong because 'show log messages' displays system log entries (syslog), which may indicate errors or events but does not provide real-time per-process CPU usage. Option B is wrong because 'show system memory' reports memory utilization statistics, not CPU consumption by individual processes. Option D is wrong because 'show interfaces' shows interface status and traffic counters, which are unrelated to identifying CPU-intensive processes.

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34

Matchingmedium

Match each Junos security feature to its description.

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

Concepts

Matches

Protects against network-based attacks

Translates private IP addresses to public IP addresses

Provides secure encrypted tunnels between sites

Controls traffic based on packet headers

Logical grouping of interfaces with security policies

Why these pairings

These are key security features in Junos.

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35

MCQeasy

An administrator is asked to check the system log files for any error messages related to interface failures. Which command would be most efficient?

A.monitor start messages | match "error"

B.show log file messages | match "error"

C.show log messages

D.show system syslog messages

AnswerB

Efficiently filters for errors in the log file.

Why this answer

Option B is correct because 'show log messages' displays the contents of the /var/log/messages file, and piping the output to 'match "error"' filters for lines containing 'error', making it the most efficient command to check system log files for interface failure errors. The 'show log' command is the standard way to view log files in JUNOS, and the 'match' filter allows targeted searching without overwhelming the administrator with irrelevant data.

Exam trap

The trap here is that candidates may confuse 'monitor start messages' with 'show log messages', thinking the real-time monitor is more efficient for checking logs, but the question asks for checking existing log files, not monitoring live events.

How to eliminate wrong answers

Option A is wrong because 'monitor start messages' is a real-time monitoring command that continuously streams new log entries to the terminal, not a static search of existing log files; it would require the administrator to wait for errors to occur and does not efficiently check historical logs. Option C is wrong because 'show log messages' displays the entire contents of the messages log file without any filtering, which is inefficient for finding specific error messages related to interface failures, especially on a busy system with many log entries. Option D is wrong because 'show system syslog messages' is not a valid JUNOS command; the correct command to view syslog configuration is 'show configuration system syslog', but this does not display log file contents or error messages.

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36

MCQhard

A company runs Juniper MX routers in a data center. They have a monitoring server that polls SNMP every 5 minutes. Recently, the monitoring server reported that interface ge-0/0/1 on router R1 has been down for 3 hours, but the network operations center says that no alarms were triggered and the link appears up from their end. The administrator logs into R1 and runs 'show interfaces ge-0/0/1' and sees that the interface is up with no errors, but the output shows 'Last flapped: 3 hours ago', which matches the monitoring downtime. Further investigation reveals that the interface has been administratively disabled and re-enabled at that time by an automated script that was later rolled back. The monitoring server uses ifAdminStatus and ifOperStatus OIDs. Which action would most reliably prevent this false positive in the future?

A.Use 'show interfaces extensive' to confirm interface status.

B.Change the SNMP polling interval to 1 minute.

C.Monitor ifLastChange OID along with ifOperStatus to detect administrative flapping.

D.Disable the automated script that caused the administrative disable.

AnswerC

ifLastChange provides the timestamp of the last interface state change. Comparing it with administrative changes helps distinguish real failures from administrative actions.

Why this answer

Option D is correct because ifLastChange provides the timestamp of the last state change. By cross-referencing ifLastChange with ifOperStatus, the monitoring system can detect that the 'down' event was administrative (ifAdminStatus changed) rather than a true link failure. Option A reduces polling interval but does not distinguish administrative changes.

Option B disables the script, which is a temporary fix and not a monitoring improvement. Option C relies on manual verification, which is not automated.

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37

MCQmedium

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

A.The OSPF interface is configured as passive

B.The hello timer is too slow

C.Authentication is missing

D.The interface is administratively down

AnswerA

Passive interfaces do not send hellos.

Why this answer

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

Exam trap

The trap here is that candidates often assume 'passive' only prevents the interface from sending routing updates (like in RIP or EIGRP), but in OSPF it blocks all Hello packets, preventing neighbor discovery entirely.

How to eliminate wrong answers

Option B is wrong because the hello timer being too slow would still allow neighbor discovery and adjacency formation, just with longer intervals; it would not result in zero neighbors. Option C is wrong because authentication is not configured in the given output, and its absence does not prevent neighbor discovery unless authentication is required on the neighbor side. Option D is wrong because 'show interfaces ge-0/0/1 terse' shows the interface is up, not administratively down.

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38

MCQhard

Your company runs a Juniper MX480 router as the core gateway. The router has been experiencing intermittent connectivity issues with a remote site over a point-to-point OC3 link. Users report that the link goes down for a few seconds several times a day. You suspect that the issue might be related to physical layer errors or framing. You need to determine the cause and collect relevant data to present to the service provider. Which course of action should you take first?

A.Run 'monitor interface so-0/0/0' and observe for any CRC errors or alarms over a period of time.

B.Perform a loopback test on the interface using 'test interface so-0/0/0'.

C.Review the system syslog file using 'show log messages' and search for interface down messages.

D.Immediately replace the serial interface card to rule out hardware failure.

AnswerA

Real-time monitoring captures transient physical layer issues.

Why this answer

Option A is correct because 'monitor interface so-0/0/0' provides real-time, continuous display of interface counters and alarms, allowing you to observe CRC errors, framing errors, or alarms (e.g., LOS, LOF) as they occur. This is the most direct way to capture transient physical-layer issues on a SONET/SDH OC3 link without disrupting service, making it the appropriate first step before escalating to the service provider.

Exam trap

The trap here is that candidates may choose the loopback test (Option B) because it is a classic troubleshooting tool, but they overlook that it is an intrusive, out-of-service test that should follow passive monitoring to avoid unnecessary downtime.

How to eliminate wrong answers

Option B is wrong because performing a loopback test ('test interface so-0/0/0') would disrupt live traffic and is typically used for out-of-service troubleshooting after initial data collection, not as a first step. Option C is wrong because reviewing the system syslog ('show log messages') may show interface down messages but lacks the granularity to capture brief, intermittent physical-layer errors like CRC or framing alarms that occur over seconds. Option D is wrong because immediately replacing the serial interface card is a premature and invasive action that should only be taken after diagnostic data (e.g., from monitoring or loopback tests) confirms a hardware fault.

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39

Multi-Selectmedium

Which two commands can be used to monitor real-time interface statistics and errors on a Junos device?

Select 2 answers

A.show interfaces terse

B.show interfaces ge-0/0/0

C.show interfaces extensive ge-0/0/0 | refresh 1

D.monitor interface ge-0/0/0

E.monitor security log

AnswersC, D

With the refresh pipe option, it provides continuous updates of extensive interface statistics.

Why this answer

Option C is correct because the 'show interfaces extensive ge-0/0/0 | refresh 1' command displays detailed interface statistics and errors, and the 'refresh 1' pipe modifier automatically updates the output every second, enabling real-time monitoring. Option D is correct because the 'monitor interface ge-0/0/0' command is specifically designed for real-time monitoring of interface counters and errors, refreshing the display at a default interval of 1 second. Both commands provide live views of interface statistics such as input/output packets, errors, drops, and CRC errors.

Exam trap

The trap here is that candidates often confuse static 'show interfaces' commands (which provide a point-in-time snapshot) with real-time monitoring commands, leading them to select option B instead of the correct real-time options C and D.

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40

Multi-Selectmedium

Which three commands can be used to view system log messages? (Choose three.)

Select 3 answers

A.show system syslog

B.show log messages

C.monitor start messages

D.show log dm

E.tail -f /var/log/messages

AnswersB, C, D

Displays messages log file.

Why this answer

Option B is correct because the 'show log messages' command displays the contents of the /var/log/messages file, which is the primary system log file on Junos OS. This file contains kernel messages, system startup events, and other critical operational logs, making it a standard way to view system log messages.

Exam trap

The trap here is that candidates may confuse the Unix shell command 'tail -f /var/log/messages' with a valid Junos CLI command, or assume 'show system syslog' is a valid operational command when it is actually a configuration context command.

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41

MCQmedium

After a software upgrade, a router fails to boot with the new image. The engineer suspects the image is corrupted. What is the recommended method to recover?

A.Insert the rescue media and boot from it, then reinstall the image

B.Delete the current configuration and reboot

C.Reboot the router multiple times

D.Use the request system software add command with the force option

AnswerA

Standard recovery procedure.

Why this answer

When a Junos OS image is corrupted and the router fails to boot, the recommended recovery method is to boot from rescue media (such as a USB flash drive or a pre-configured rescue partition) and then reinstall the correct image. This bypasses the corrupted software on the internal storage and provides a clean environment for recovery, ensuring the router can be restored to a functional state.

Exam trap

The trap here is that candidates may think the 'request system software add' command with the 'force' option can recover a corrupted image while the router is still booting, but this command requires a running Junos OS, which is unavailable when the image is corrupted.

How to eliminate wrong answers

Option B is wrong because deleting the current configuration does not address a corrupted image; the router cannot boot without a valid OS, and configuration is irrelevant at this stage. Option C is wrong because rebooting multiple times will not repair a corrupted image; it only repeats the same boot failure. Option D is wrong because the 'request system software add' command requires the router to be booted and operational, which is impossible if the image is corrupted and the router cannot boot; the 'force' option does not bypass the need for a running system.

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42

MCQmedium

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

A.request system configuration rescue save

B.request system reboot

C.request system reboot at 03:00

D.load override /config/juniper.conf.gz

AnswerC

Schedules reboot at specified time.

Why this answer

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

Exam trap

The trap here is that candidates often confuse 'request system reboot' (immediate reboot) with 'request system reboot at' (scheduled reboot), or they mistakenly think that loading a configuration file will trigger a reboot.

How to eliminate wrong answers

Option A is wrong because 'request system configuration rescue save' is used to save the current active configuration as a rescue configuration, which can be used to recover the device if the configuration becomes corrupted; it does not schedule or perform a reboot. Option B is wrong because 'request system reboot' without any time parameter triggers an immediate reboot of the device, not a scheduled reboot at 3:00 AM. Option D is wrong because 'load override /config/juniper.conf.gz' is a configuration mode command used to replace the current candidate configuration with the configuration stored in the specified file; it does not schedule or initiate a reboot.

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43

MCQhard

An engineer needs to check if the device has any pending changes that have not been committed. Which operational command should they run?

A.show system configuration

B.show system rollback

C.show configuration | compare

D.show system commit

AnswerC

Shows uncommitted configuration differences.

Why this answer

Option C is correct because the 'show configuration | compare' command displays the differences between the candidate configuration (changes made but not yet committed) and the active configuration. This allows the engineer to see any pending changes that have not been committed, which is exactly what the question asks.

Exam trap

The trap here is that candidates often confuse 'show system commit' (which shows commit history) with showing pending changes, or they think 'show configuration' alone shows uncommitted changes, but without the '| compare' pipe it only shows the active configuration.

How to eliminate wrong answers

Option A is wrong because 'show system configuration' is not a valid Junos operational command; the correct command to view the active configuration is 'show configuration'. Option B is wrong because 'show system rollback' displays a list of previous committed configurations (rollback snapshots), not pending uncommitted changes. Option D is wrong because 'show system commit' shows the commit history (log of past commits), not any uncommitted changes in the candidate configuration.

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44

MCQhard

A network engineer needs to analyze NTP synchronization status and offset. Which command provides detailed NTP peer information including delay, offset, and jitter?

A.show ntp statistics

B.show ntp associations

C.show ntp status

D.show ntp peer

AnswerB

Displays peer address, delay, offset, jitter, and stratum.

Why this answer

The 'show ntp associations' command displays detailed NTP peer information, including delay, offset, and jitter, which are essential for analyzing synchronization status. This command lists all configured NTP peers and their current state, providing the specific metrics needed to assess clock accuracy and stability.

Exam trap

The trap here is that candidates familiar with Cisco IOS may expect 'show ntp peer' to work, but Junos uses 'show ntp associations' for the same detailed peer information, while 'show ntp peer' is not a valid command.

How to eliminate wrong answers

Option A is wrong because 'show ntp statistics' displays NTP packet statistics (e.g., packets sent/received, dropped) rather than per-peer delay, offset, and jitter. Option C is wrong because 'show ntp status' shows the local NTP daemon status (e.g., clock stratum, reference ID) but not detailed peer-level metrics. Option D is wrong because 'show ntp peer' is not a valid Junos command; the correct command for peer details is 'show ntp associations'.

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45

Multi-Selectmedium

Which TWO statements are correct about the 'monitor interface' command?

Select 2 answers

A.It displays output in real-time

B.It shows a static snapshot

C.It can be terminated with Ctrl+C

D.It requires a 'start' parameter

E.It provides historical statistics

AnswersA, C

Continuously updates with new data.

Why this answer

The 'monitor interface' command in Junos OS displays real-time statistics for the specified interface, updating continuously until the user terminates it. This is why option A is correct: it provides a live, dynamic view of interface counters like packets, errors, and bandwidth utilization.

Exam trap

The trap here is that candidates confuse 'monitor interface' with 'show interface' — the former is real-time and continuous, while the latter provides a static snapshot at a single point in time.

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46

MCQeasy

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

A.show configuration

B.show interfaces

C.request support information

D.show route

AnswerC

Gathers comprehensive system data for troubleshooting.

Why this answer

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

Exam trap

The trap here is that candidates often confuse individual show commands (like 'show route' or 'show interfaces') with the all-in-one 'request support information' command, failing to recognize that only the latter captures the full system state required for a support ticket.

How to eliminate wrong answers

Option A is wrong because 'show configuration' only displays the current active configuration, not the dynamic operational state like routing tables or interface statistics. Option B is wrong because 'show interfaces' only shows interface status and counters, missing routing tables and configuration. Option D is wrong because 'show route' only displays the routing table, omitting interfaces and configuration data.

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47

MCQmedium

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

A.commit check

B.show configuration

C.show system configuration

D.show | compare

AnswerD

The 'show | compare' command displays differences between the candidate and active configurations. If no differences are shown, the configurations are identical.

Why this answer

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

Exam trap

The trap here is that candidates often confuse `commit check` (which only validates syntax) with a comparison command, leading them to select Option A, but `commit check` does not compare the candidate to the active configuration.

How to eliminate wrong answers

Option A is wrong because `commit check` validates the syntax and semantics of the candidate configuration but does not compare it to the active configuration; it only ensures the candidate can be committed without errors. Option B is wrong because `show configuration` displays the candidate configuration (or the active if no candidate changes exist), but it does not perform a comparison with the active configuration. Option C is wrong because `show system configuration` is not a valid Junos command; the correct command to view system configuration is `show configuration` or `show system` with specific filters.

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48

MCQhard

You are managing a Juniper MX router that serves as a BGP route reflector for multiple customer VPNs. The router has two routing engines (RE0 and RE1) in a graceful switchover (GRES) configuration. During a routine maintenance window, you need to upgrade the Junos OS from version 18.1R1 to 20.2R2. The upgrade must minimize traffic disruption. You have already staged the new image on both REs. Which sequence of commands ensures minimal impact?

A.On RE0: request system software add jinstall-20.2R2.tgz reboot; then on RE1 same command

B.On RE0: request system reboot (without adding software)

C.On RE1: request system software add jinstall-20.2R2.tgz reboot; after reboot, on RE0: request chassis routing-engine master switch; then request system software add jinstall-20.2R2.tgz reboot

D.On both REs: request system software add jinstall-20.2R2.tgz reboot

AnswerC

Minimizes downtime by upgrading backup first, then switching.

Why this answer

Option C is correct because it performs a non-disruptive upgrade by first upgrading the backup RE (RE1), then switching mastership to the upgraded RE, and finally upgrading the original master RE. This sequence leverages Graceful Routing Engine Switchover (GRES) to maintain BGP sessions and VPN forwarding during the upgrade, minimizing traffic disruption.

Exam trap

The trap here is that candidates assume rebooting both REs sequentially with the same command is sufficient, but they overlook the need to switch mastership to the upgraded backup RE before upgrading the original master to avoid a double-reboot scenario that disrupts traffic.

How to eliminate wrong answers

Option A is wrong because rebooting both REs sequentially without first switching mastership causes a full outage when the master RE reboots, as the backup RE is not yet upgraded and may not take over cleanly. Option B is wrong because rebooting without adding the new software does not perform an upgrade, leaving the router on the old version. Option D is wrong because adding the software and rebooting both REs simultaneously or without proper mastership control can cause a complete loss of routing and forwarding, as both REs may reboot at the same time or the backup RE cannot take over gracefully.

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49

MCQmedium

A network engineer is performing a software upgrade on an MX router. Before upgrading, which operational command should be used to verify the current software version and the upgrade file?

A.show configuration system software

B.show system upgrade

C.show system software

D.show version

AnswerD

Shows current software version; used with 'request system software validate' for image check.

Why this answer

The 'show version' command displays the currently running Junos OS version, including the software build and release information. Before upgrading, you must verify the current version to ensure compatibility with the upgrade file, and the upgrade file itself is typically referenced by its filename or path, not shown by this command. To check the upgrade file, you would use 'file list' or 'show system software' to list available packages, but for the current version, 'show version' is the correct operational command.

Exam trap

The trap here is that candidates confuse 'show system software' (which lists installed packages) with 'show version' (which shows the running kernel), leading them to choose C, but only 'show version' directly answers the question of the current software version.

How to eliminate wrong answers

Option A is wrong because 'show configuration system software' is not a valid Junos command; configuration is displayed using 'show configuration' or 'show | display set', and software settings are under 'system' hierarchy but not with that syntax. Option B is wrong because 'show system upgrade' is not a valid Junos operational command; Junos uses 'request system software add' for upgrades and 'show system software' for package information. Option C is wrong because 'show system software' displays installed software packages and their versions, but it does not show the currently running Junos kernel version; 'show version' is the standard command for the active software release.

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50

MCQeasy

A network administrator wants to view the current configuration that is actively running on a Juniper device. Which operational mode command should be used?

A.show configuration

B.show running-config

C.show active-config

D.show current-config

AnswerA

Displays the current active configuration.

Why this answer

In Junos OS, the operational mode command 'show configuration' displays the active, committed configuration currently running on the device. Unlike Cisco IOS, Junos does not use a separate 'running-config'; instead, the configuration is stored as a single candidate configuration that becomes active only after a 'commit' operation. Thus, 'show configuration' is the correct command to view the active configuration.

Exam trap

The trap here is that candidates familiar with Cisco IOS may instinctively choose 'show running-config', but Junos uses a different paradigm with 'show configuration' to display the active committed configuration.

How to eliminate wrong answers

Option B is wrong because 'show running-config' is a Cisco IOS command, not a valid Junos operational mode command; Junos uses 'show configuration' to display the active configuration. Option C is wrong because 'show active-config' is not a valid Junos command; Junos does not have an 'active-config' keyword in its operational mode. Option D is wrong because 'show current-config' is not a valid Junos command; Junos uses 'show configuration' as the standard command to view the current active configuration.

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51

MCQeasy

Refer to the exhibit. An administrator notices the /var partition is nearly full. Which command can be used to safely reclaim disk space?

A.request system reboot

B.request system storage cleanup

C.delete /var/log/messages

D.request system software delete

AnswerB

The 'request system storage cleanup' command safely removes temporary files, old logs, core files, and software images from /var and other partitions, freeing up space without risking critical data.

Why this answer

The 'request system storage cleanup' command safely removes old log files, core dumps, and other temporary files that are no longer needed, freeing up space on the /var partition without risking system stability. This is the recommended Junos method for reclaiming disk space because it targets only files that can be safely deleted.

Exam trap

The trap here is that candidates may think manually deleting log files (option C) is safe and effective, but Junos relies on its own cleanup mechanisms to avoid breaking log rotation or losing important diagnostic data.

How to eliminate wrong answers

Option A is wrong because 'request system reboot' only restarts the system and does not delete any files, so it will not reclaim disk space. Option C is wrong because manually deleting '/var/log/messages' can cause loss of critical logging data and may not be safe if the file is still being written to; Junos manages log rotation automatically, and direct deletion can disrupt that. Option D is wrong because 'request system software delete' is used to remove installed software packages, not to clean up temporary or log files, and it could inadvertently remove needed software.

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52

MCQmedium

A technician needs to monitor routing table updates in real time. Which command provides continuous output of routing changes?

A.monitor route

B.show log messages | match route

C.show route

D.show route protocol bgp

AnswerA

Provides continuous updates of routing changes.

Why this answer

The 'monitor route' command in Junos provides a real-time, continuously updating view of routing table changes as they occur. Unlike static commands that show a snapshot, this command actively tracks route additions, removals, and modifications, making it the correct choice for monitoring routing updates in real time.

Exam trap

The trap here is that candidates often confuse 'monitor route' with 'show route' or filtered log commands, assuming any command with 'route' or 'log' can provide real-time output, but only 'monitor route' offers continuous, live updates in Junos.

How to eliminate wrong answers

Option B is wrong because 'show log messages | match route' displays historical log entries filtered for the word 'route', not a continuous real-time stream of routing changes. Option C is wrong because 'show route' outputs a static snapshot of the current routing table, not a live update feed. Option D is wrong because 'show route protocol bgp' shows only BGP-learned routes in a static format, lacking the continuous monitoring capability required.

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53

MCQhard

Refer to the exhibit. What is the most likely cause of the BGP session failure?

A.Hold timer expired due to delayed keepalives

B.The peer is unreachable

C.BGP configuration mismatch

D.Route flapping

AnswerA

The log clearly states 'Hold time expired'.

Why this answer

The BGP session failure is most likely due to the hold timer expiring because keepalive messages were not received in time. In JUNOS, the default hold time is 90 seconds, and if a router does not receive a keepalive or update within that interval, it declares the peer dead and resets the session. The exhibit shows the BGP state as 'Idle' or 'Active', which is consistent with a hold timer expiry event.

Exam trap

The trap here is that candidates often assume a BGP session failure is always due to a configuration mismatch or unreachable peer, but the hold timer expiry is a common operational issue caused by delayed keepalives, which is a key concept in BGP session maintenance.

How to eliminate wrong answers

Option B is wrong because if the peer were unreachable, the BGP session would typically show 'Active' state indefinitely, but the hold timer expiry is a more specific cause given the session failure. Option C is wrong because a BGP configuration mismatch (e.g., AS number mismatch) would result in a 'Notification' message or 'Idle' state with a specific error code, not a hold timer expiry. Option D is wrong because route flapping affects the stability of routes but does not directly cause the BGP session itself to fail; it would trigger route withdrawals and updates, not a hold timer expiry.

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54

MCQhard

A service provider has two MX routers (R1 and R2) connected via two separate physical links. Both links are in an aggregated Ethernet bundle (ae0). The ae0 interface is configured with LACP active on both sides. Recently, a fiber cut occurred on one of the member links, and the aggregated interface continued working. However, after the fiber was repaired, the network operator noticed that the restored link is not being re-added to the bundle. 'show lacp interfaces' indicates the link is in a 'detached' state. The operator checks 'show interfaces diagnostics optics' and finds that the optical parameters are normal. Which action should the operator take to restore the link to the bundle without affecting traffic?

A.Reboot the router to clear all LACP states

B.Remove and re-add the member link from the ae0 configuration

C.Issue the 'clear lacp statistics' command on the interface to reset LACP negotiation on that link

D.Replace the SFP module on the restored link

AnswerC

Clearing LACP statistics resets the LACP state machine, allowing the link to re-negotiate and join the bundle.

Why this answer

Option C is correct because the 'detached' state in LACP indicates that the link is physically up but LACP negotiation has failed or is stuck. The 'clear lacp statistics' command resets the LACP state machine on the specified interface, forcing it to re-initiate LACP PDUs and renegotiate with the peer. This restores the link to the bundle without disrupting active traffic on other member links.

Exam trap

The trap here is that candidates assume a physical layer issue (like a bad SFP) or a configuration change is needed, when in fact the problem is a stuck LACP state machine that can be resolved with a non-disruptive clear command.

How to eliminate wrong answers

Option A is wrong because rebooting the router is an unnecessarily disruptive action that would affect all traffic, not just the problematic link, and is not required to clear a per-interface LACP state. Option B is wrong because removing and re-adding the member link from the ae0 configuration would cause a brief traffic interruption on that link and is an operational overhead; the issue is a software state problem, not a configuration mismatch. Option D is wrong because the operator has already verified that optical parameters are normal via 'show interfaces diagnostics optics', indicating the SFP module and physical layer are healthy, so replacing the SFP would not resolve the LACP state machine issue.

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55

Multi-Selecthard

Which TWO commands can be used to view the current routing table entries for IPv4 unicast routes?

Select 2 answers

A.show route protocol static

B.show route table inet.0

C.show forwarding-table

D.show route

E.show route table inet6.0

AnswersB, D

'show route table inet.0' explicitly displays the IPv4 unicast routing table. This is equivalent to 'show route' but more specific.

Why this answer

Option B is correct because `show route table inet.0` explicitly displays the IPv4 unicast routing table (inet.0) in Junos. Option D is correct because `show route` without any filter defaults to showing all routes in the inet.0 table, which is the primary IPv4 unicast routing table.

Exam trap

The trap here is that candidates confuse the routing table (`show route`) with the forwarding table (`show forwarding-table`), or assume a specific protocol filter like `protocol static` shows all routes, when in fact it only shows routes learned via that protocol.

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56

MCQmedium

Refer to the exhibit. An engineer notices that input drops are increasing. What is the most likely cause?

A.Speed mismatch

B.Buffer overflow

C.Cable fault

D.CRC errors

AnswerB

Input drops indicate buffer overflow or congestion.

Why this answer

Input drops occur when the ingress interface's receive buffer is full and cannot accept more packets, typically due to the ingress rate exceeding the interface's ability to process or forward packets to the internal switch fabric. In Junos, this is often caused by microbursts or sustained oversubscription, not by a speed mismatch (which would show as errors or link flaps) or cable faults (which cause physical-layer errors). Buffer overflow is the correct answer because input drops directly indicate that the packet buffer has been exhausted.

Exam trap

The trap here is that candidates often confuse input drops with CRC errors or assume a speed mismatch is the cause, but Junos explicitly separates input drops (buffer overflow) from physical-layer errors, and the question's exhibit would show no CRC errors or link flaps, isolating the issue to buffer exhaustion.

How to eliminate wrong answers

Option A is wrong because a speed mismatch between two connected interfaces would typically cause the link to not come up or generate extensive CRC/alignment errors, not specifically input drops. Option C is wrong because a cable fault usually manifests as CRC errors, frame errors, or link flaps, not as a steady increase in input drops. Option D is wrong because CRC errors are a separate counter indicating data corruption at the physical layer, often due to signal integrity issues, and are not the direct cause of input drops.

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57

MCQeasy

A technician needs to view the last 50 log messages from the system log file. Which command accomplishes this?

A.show system log messages

B.monitor start messages

C.show system syslog

D.show log messages | last 50

AnswerD

The 'show log messages' command displays log entries from the messages file, and piping with '| last 50' shows the last 50 lines. This is the proper way to view recent log messages.

Why this answer

Option D is correct because the 'show log messages | last 50' command displays the last 50 lines from the /var/log/messages file on a Junos device. The pipe to 'last' is a Junos CLI filter that outputs only the final N lines of the command output, which is exactly what is needed to view the most recent log entries.

Exam trap

The trap here is that candidates confuse the 'show log' command with 'show system syslog' or 'show system log messages', misremembering the exact syntax for viewing log file contents versus configuration.

How to eliminate wrong answers

Option A is wrong because 'show system log messages' is not a valid Junos command; the correct command to view the system log file is 'show log messages'. Option B is wrong because 'monitor start messages' is used to tail the log file in real time, not to view a static set of the last 50 messages. Option C is wrong because 'show system syslog' displays the syslog configuration, not the actual log file contents.

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58

MCQmedium

Refer to the exhibit. An engineer is trying to commit a configuration but receives a 'no space left on device' error. Which filesystem is most likely full?

A./config

B./tmp

C./dev

D./var

AnswerD

/var is at 100% capacity, causing no space left error.

Why this answer

The /var filesystem on Junos stores log files, core dumps, and other operational data. When the device runs out of disk space, it is most commonly the /var partition that is full, as it accumulates logs and crash files over time. The 'no space left on device' error during a commit indicates that the system cannot write the new configuration to the /var/tmp or /var/db/config directory, which reside under /var.

Exam trap

The trap here is that candidates often assume the /config filesystem is the one that stores configurations and thus must be full, but in Junos, the commit process uses /var/tmp as a staging area, making /var the most likely culprit when a commit fails due to disk space.

How to eliminate wrong answers

Option A is wrong because /config is a separate partition that stores the active and backup configurations, and it is rarely the cause of a 'no space left on device' error during a commit; it is typically small and only fills if configurations are excessively large. Option B is wrong because /tmp is a memory-backed filesystem (tmpfs) used for temporary files and is not persistent; it is not where commit operations write configuration data. Option C is wrong because /dev is a virtual filesystem for device nodes and does not store configuration or log files; it cannot become full in the traditional sense.

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59

MCQmedium

Refer to the exhibit. Which interface(s) have a physical layer issue?

A.ge-0/0/1 only

B.ge-0/0/0 only

C.ge-0/0/0 and ge-0/0/2

D.ge-0/0/2 only

AnswerA

ge-0/0/1 has link down while admin up, indicating physical issue.

Why this answer

The 'Physical link is Down' status on ge-0/0/1 indicates a Layer 1 issue, such as a disconnected cable, faulty transceiver, or powered-down remote device. The other interfaces show 'Up' physical status, confirming they have no physical layer problem.

Exam trap

The trap here is that candidates may confuse 'Physical link is Down' with an administrative 'down' state, but the output clearly shows 'up' in the admin column, so the issue is purely physical layer, not configuration-based.

How to eliminate wrong answers

Option B is wrong because ge-0/0/0 shows 'Physical link is Up', meaning its physical layer is operational. Option C is wrong because both ge-0/0/0 and ge-0/0/2 have 'Physical link is Up', so neither has a physical layer issue. Option D is wrong because ge-0/0/2 shows 'Physical link is Up', indicating no physical layer problem.

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60

MCQmedium

A technician notices that the /var partition is filling up on a Juniper device. Which action would be most appropriate to free up space while preserving critical logs?

A.Delete core files manually

B.Run 'request system storage cleanup'

C.Reboot the device

D.Delete all files in /var/log

AnswerB

The 'request system storage cleanup' command safely removes temporary and unnecessary files like old log files, core files, and software images. It preserves important logs.

Why this answer

The 'request system storage cleanup' command is the correct action because it safely removes non-essential files such as old log files, core dumps, and temporary files that are no longer needed, while preserving critical logs and configuration files. This command performs a controlled cleanup without risking the deletion of important operational data, making it the most appropriate method for freeing up space on the /var partition.

Exam trap

The trap here is that candidates often assume manual deletion (Option A) or a reboot (Option C) are quick fixes, but they overlook the Junos-specific safe cleanup command that automates the process while preserving essential data.

How to eliminate wrong answers

Option A is wrong because manually deleting core files is risky and inefficient; core files may be needed for debugging, and manual deletion could accidentally remove files that are still in use or miss other space-consuming temporary files. Option C is wrong because rebooting the device does not free up disk space; it only clears temporary memory and may cause unnecessary downtime without addressing the underlying storage issue. Option D is wrong because deleting all files in /var/log would remove critical logs needed for troubleshooting and compliance, and it could also delete active log files that are still being written to, potentially causing system instability or loss of forensic data.

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61

Multi-Selecthard

Which three steps are part of a typical software upgrade process on a Juniper device? (Choose three.)

Select 3 answers

A.Issue the request system software add command

B.Download the image to /var/tmp

C.Shut down all interfaces

D.Delete the old image before adding the new one

E.Reboot the device

AnswersA, B, E

Adds the software package.

Why this answer

Option A is correct because the 'request system software add' command is the standard Junos CLI command used to initiate the installation of a new software image on a Juniper device. This command triggers the process of copying the image from a specified source (e.g., a URL or local file) into the system's active software partition, preparing it for the next reboot.

Exam trap

The trap here is that candidates may mistakenly think interfaces must be shut down before an upgrade (option C), confusing Junos' non-disruptive upgrade process with Cisco IOS procedures where manual interface shutdown is often recommended to prevent routing flaps during the reload.

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62

MCQeasy

Which command displays the status of all configured interfaces, including administrative and operational status?

A.show interfaces terse

B.show configuration interfaces

C.show chassis hardware

D.show interface statistics

AnswerA

'show interfaces terse' displays all interfaces with administrative (Admin) and operational (Link) status in a concise format. It clearly shows which interfaces are up or down.

Why this answer

The 'show interfaces terse' command displays a concise summary of all interfaces, including their administrative status (up or down) and operational status (up or down), along with protocol states. This makes it the correct choice for quickly viewing the status of all configured interfaces in a single output.

Exam trap

The trap here is that candidates often confuse 'show interfaces terse' with 'show interface statistics' or 'show configuration interfaces', mistakenly thinking statistics or configuration output will show operational status, but only 'show interfaces terse' provides the concise admin and link status in a single view.

How to eliminate wrong answers

Option B is wrong because 'show configuration interfaces' displays the current configuration of interfaces, not their real-time operational or administrative status. Option C is wrong because 'show chassis hardware' shows physical hardware components (like FPCs, PICs, and power supplies), not interface status. Option D is wrong because 'show interface statistics' shows traffic counters and error statistics for interfaces, but does not explicitly display administrative or operational status in a summary format.

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63

MCQmedium

A network engineer suspects a hardware issue on an interface. Which command provides the most detailed hardware error counters, including CRC errors, framing errors, and runts?

A.show interfaces diagnostics optics

B.show interfaces detail

C.show interfaces extensive

D.show log messages

AnswerC

'show interfaces extensive' provides detailed statistics per interface, including input errors such as CRC, framing, runts, and output errors. It is the best command for hardware error analysis.

Why this answer

The 'show interfaces extensive' command provides the most detailed hardware error counters for a Junos interface, including CRC errors, framing errors, and runts. This command displays per-interface statistics at the physical layer, such as input errors, output errors, and specific error types like frame, runts, giants, and CRC errors, which are essential for diagnosing hardware issues.

Exam trap

The trap here is that candidates often confuse 'show interfaces detail' with 'show interfaces extensive', assuming 'detail' provides the most granular error counters, but only 'extensive' includes the full hardware error breakdown required for hardware fault diagnosis.

How to eliminate wrong answers

Option A is wrong because 'show interfaces diagnostics optics' is used to display optical transceiver diagnostics (e.g., temperature, voltage, laser bias) and does not show interface error counters like CRC or framing errors. Option B is wrong because 'show interfaces detail' provides more information than the basic output but does not include the extensive hardware error counters; it omits the per-error-type breakdown found in the extensive output. Option D is wrong because 'show log messages' displays system log messages, not real-time interface hardware error counters; it is used for troubleshooting events and errors logged by the system, not for granular interface statistics.

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64

Multi-Selecteasy

Which TWO commands can be used to view the system log messages on a Juniper device? (Select two.)

Select 2 answers

A.show log dcd

B.show log messages

C.monitor start messages

D.show log file

E.show system messages

AnswersB, C

Displays and tails the current log messages.

Why this answer

Option B is correct because 'show log messages' displays the contents of the default system log file, /var/log/messages, which contains kernel, daemon, and system-level messages. Option C is correct because 'monitor start messages' provides a real-time tail of the same /var/log/messages file, allowing live monitoring of system log entries as they are written.

Exam trap

The trap here is that candidates confuse the generic 'show log' syntax with a nonexistent 'show log file' command, or they mistakenly think 'show system messages' is valid because of similarity to other vendors' commands like 'show logging' on Cisco IOS.

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65

Multi-Selectmedium

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

Select 2 answers

A.show ip route

B.show route protocol ospf

C.show route

D.show route table inet.0

E.show routing

AnswersC, D

Shows the default routing table (inet.0).

Why this answer

Option C is correct because the 'show route' command without any filters displays the entire IPv4 unicast routing table (inet.0) by default in Junos OS. Option D is correct because 'show route table inet.0' explicitly targets the main IPv4 unicast routing table, which is the default routing instance's inet.0 table.

Exam trap

The trap here is that candidates familiar with Cisco IOS may incorrectly choose 'show ip route' (Option A) or 'show routing' (Option E), not realizing Junos uses the 'show route' command and organizes routing information into named tables like inet.0.

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66

MCQhard

A network technician needs to clear all BGP sessions and force BGP to re-establish peering relationships. Which command should they use?

A.clear bgp summary

B.clear bgp restart

C.clear bgp all

D.clear bgp statistics

AnswerC

Clears all BGP sessions, causing re-establishment.

Why this answer

Option C is correct because the 'clear bgp all' command in Junos resets all BGP sessions by clearing the BGP routing table and forcing the protocol to re-establish peering relationships from scratch. This is the standard Junos command to tear down and restart all BGP adjacencies, triggering new OPEN messages and route exchanges.

Exam trap

The trap here is that candidates familiar with Cisco IOS might expect 'clear ip bgp *' to be the equivalent, but Junos uses 'clear bgp all' instead, and the wrong options mimic Cisco-style commands that do not exist or have different effects in Junos.

How to eliminate wrong answers

Option A is wrong because 'clear bgp summary' only clears the BGP summary statistics counters (e.g., number of prefixes received/sent) without affecting BGP sessions or peering state. Option B is wrong because 'clear bgp restart' is not a valid Junos command; Junos uses 'restart' as a routing protocol process restart (e.g., 'restart routing'), not for BGP sessions. Option D is wrong because 'clear bgp statistics' clears BGP statistics and counters but does not reset or re-establish BGP peering sessions.

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67

Multi-Selecthard

Which THREE commands are used for operational monitoring of routing protocols?

Select 3 answers

A.show isis adjacency

B.show ospf neighbor

C.show interfaces terse

D.show bgp summary

E.show arp

AnswersA, B, D

Shows IS-IS adjacencies.

Why this answer

The 'show isis adjacency' command is used to verify the state of IS-IS neighbor adjacencies, which is a core operational monitoring task for the IS-IS routing protocol. It displays the interface, neighbor system ID, level, and adjacency state (e.g., Up, Down, Initializing), allowing an engineer to confirm that IS-IS neighbors are properly established.

Exam trap

The trap here is that candidates may confuse general interface or Layer 2 monitoring commands (like 'show interfaces terse' or 'show arp') with protocol-specific operational monitoring commands, leading them to select options that do not actually show routing protocol state.

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68

MCQmedium

A junior administrator wants to view only the operational state of interface ge-0/0/1, including its link status and protocol state. Which command should they use?

A.show interface ge-0/0/1

B.show interfaces ge-0/0/1 terse

C.show configuration interfaces ge-0/0/1

D.show interfaces ge-0/0/1 extensive

AnswerB

Shows link and protocol status in brief format.

Why this answer

Option B is correct because the 'show interfaces ge-0/0/1 terse' command displays a concise operational state of the interface, including link status (up/down) and protocol state (up/down) without configuration details. This is the standard Junos command for quickly verifying the operational status of a specific interface.

Exam trap

The trap here is that candidates familiar with Cisco IOS might type 'show interface' (singular) instead of the Junos plural 'show interfaces', or they might choose 'extensive' thinking more detail is better, when 'terse' is the precise tool for a quick operational state check.

How to eliminate wrong answers

Option A is wrong because 'show interface ge-0/0/1' is an invalid command in Junos; the correct syntax uses the plural 'interfaces'. Option C is wrong because 'show configuration interfaces ge-0/0/1' displays the configuration stanza for the interface, not its operational state. Option D is wrong because 'show interfaces ge-0/0/1 extensive' provides detailed operational and statistical data, which is more than the junior administrator needs for just link and protocol state.

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69

MCQhard

During a network outage, a router is unresponsive via SSH. You have console access but the console displays 'Amnesiac (ttyd0)' prompt. What is the most likely cause and recovery action?

A.The router lost its configuration; load the rescue configuration using 'rollback rescue-config' or 'load override /config/rescue.conf.gz' then commit

B.The router's boot device failed; need to replace hardware

C.The router booted from backup media; run 'request system software add' to reinstall Junos

D.The router's flash memory is corrupted; perform a full reinstall via USB

AnswerA

The 'Amnesiac' prompt occurs when Junos boots but finds no valid configuration, often after 'request system zeroize' or storage failure. Loading the rescue configuration is the standard recovery procedure.

Why this answer

The 'Amnesiac (ttyd0)' prompt indicates the router has booted without a valid configuration file in the /config directory. This typically occurs after a 'request system zeroize' command, a failed commit that corrupted the configuration, or a storage issue that prevented the configuration from loading. The recovery action is to load a previously saved rescue configuration using 'rollback rescue-config' or 'load override /config/rescue.conf.gz' and then commit, which restores the router to a known working state.

Exam trap

The trap here is that candidates confuse the 'Amnesiac' prompt with a hardware failure or boot media issue, when it is actually a configuration recovery scenario that can be resolved with a simple rollback to the rescue configuration.

How to eliminate wrong answers

Option B is wrong because a boot device failure would prevent the router from booting entirely, not just cause a missing configuration; the 'Amnesiac' prompt specifically indicates the OS loaded but no config was found. Option C is wrong because booting from backup media (e.g., alternate boot device) would still load the configuration if it exists; the prompt indicates a missing config, not a boot media issue, and 'request system software add' is for installing or upgrading Junos, not for recovering a lost configuration. Option D is wrong because flash memory corruption would likely cause boot failures or file system errors, not a clean boot to the 'Amnesiac' prompt; a full reinstall via USB is an extreme measure that is unnecessary when a rescue configuration is available.

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70

MCQhard

An operator wants to monitor the temperature and voltage sensors on a Juniper chassis. Which command displays current sensor readings?

A.show chassis environment

B.show chassis hardware

C.show system health

D.show log messages | match temperature

AnswerA

'show chassis environment' displays temperature, voltage, and fan status for the chassis components. It is the standard command for environmental monitoring.

Why this answer

The 'show chassis environment' command displays real-time sensor readings for temperature, voltage, and fan status on Juniper devices. It is the standard operational command for monitoring chassis environmental health, directly matching the operator's requirement to check temperature and voltage sensors.

Exam trap

The trap here is that candidates may confuse 'show chassis hardware' (static inventory) with 'show chassis environment' (dynamic sensor data), or assume 'show system health' is a valid Junos command when it is not.

How to eliminate wrong answers

Option B is wrong because 'show chassis hardware' lists installed components (like FRUs, serial numbers, and part numbers) but does not display dynamic sensor readings such as temperature or voltage. Option C is wrong because 'show system health' is not a valid Junos command; the correct command for system health checks is 'request system health' or 'show chassis environment'. Option D is wrong because 'show log messages | match temperature' filters system log messages for temperature-related entries, but it does not show current sensor readings—it only displays historical log events that may be outdated or incomplete.

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71

MCQeasy

A network administrator notices that the CPU utilization on an MX240 router has been consistently above 90% for the past hour. Users are reporting intermittent connectivity issues. The administrator logs in and runs 'show system processes extensive' which shows the Routing Protocol Daemon (rpd) consuming 70% of the CPU. Further investigation reveals that the router has over 5000 BGP prefixes from multiple peers. The administrator suspects that the high CPU is due to continuous route processing. What should the administrator do to immediately reduce CPU load while maintaining network stability?

A.Perform a 'show log messages' to check for errors before taking action

B.Apply a prefix-limit on each BGP session to restrict the number of prefixes received

C.Bounce all BGP sessions by clearing them with 'clear bgp neighbor *'

D.Disable BGP multipath to reduce route processing

AnswerB

Prefix limits reduce the number of routes rpd must process, directly lowering CPU usage.

Why this answer

Applying a prefix-limit on each BGP session immediately restricts the number of prefixes the router will accept from peers. This prevents the Routing Protocol Daemon (rpd) from processing excessive BGP updates, reducing CPU load while maintaining network stability by keeping existing sessions and routes intact. The prefix-limit action (e.g., with a teardown threshold) ensures the router does not accept more prefixes than it can handle, directly addressing the root cause of high CPU usage.

Exam trap

The trap here is that candidates may confuse diagnostic actions (like checking logs) or disruptive resets (like clearing all BGP sessions) with immediate corrective measures, overlooking the targeted, non-disruptive solution of applying prefix limits to control route processing load.

How to eliminate wrong answers

Option A is wrong because checking logs ('show log messages') is a diagnostic step that does not reduce CPU load; it only gathers information, which is not an immediate action to alleviate the high CPU caused by continuous route processing. Option C is wrong because bouncing all BGP sessions with 'clear bgp neighbor *' would temporarily drop all BGP peers, causing a complete loss of routing information and network instability, and the CPU spike would likely recur when sessions re-establish and process the same 5000+ prefixes again. Option D is wrong because disabling BGP multipath does not reduce the number of prefixes being processed; it only affects how multiple equal-cost paths are used for forwarding, not the volume of route processing by rpd.

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72

Multi-Selectmedium

Which TWO statements correctly describe the use of the 'monitor traffic' command in Junos?

Select 2 answers

A.It captures packets from the Routing Engine only.

B.It can filter packets using the 'matching' option to capture only specific traffic.

C.It captures packets on a specific interface and displays them in real-time.

D.It requires a reboot to start capturing packets.

E.It reads packets from a previously saved pcap file.

AnswersB, C

Correct: 'monitor traffic matching <protocol>' filters packets.

Why this answer

Option B is correct because the 'monitor traffic' command in Junos supports a 'matching' option that allows you to specify a filter (e.g., 'matching "icmp"') to capture only packets that match the given criteria, reducing noise and focusing on specific traffic types. Option C is correct because 'monitor traffic interface <interface-name>' captures packets on a specified interface and displays them in real-time, which is useful for live troubleshooting.

Exam trap

The trap here is that candidates often confuse 'monitor traffic' with 'monitor interface' or assume it requires a reboot, but Junos captures live traffic without any system restart, and the 'matching' option is a powerful BPF-based filter that works exactly like tcpdump's filter syntax.

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73

MCQmedium

A technician is troubleshooting a connectivity issue and needs to see the path packets take to a remote host. Which Junos command is appropriate?

A.traceroute

B.monitor interface

C.ping

D.show route

AnswerA

Traces the path to the remote host.

Why this answer

The `traceroute` command in Junos is the correct tool for tracing the path packets take to a remote host. It sends UDP probes with increasing TTL values and listens for ICMP Time Exceeded messages from intermediate routers, revealing each hop along the route. This directly matches the technician's need to see the path packets take.

Exam trap

The trap here is that candidates often confuse `ping` (which tests reachability) with `traceroute` (which shows the path), leading them to select ping when the question explicitly asks for the path packets take.

How to eliminate wrong answers

Option B is wrong because `monitor interface` is used to display real-time interface statistics and traffic counters, not to trace the path packets take to a remote host. Option C is wrong because `ping` only tests reachability and measures round-trip time to a destination, but it does not reveal the specific hops or path taken. Option D is wrong because `show route` displays the local routing table entries on the Junos device, not the actual path packets traverse through the network to a remote host.

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74

MCQhard

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

A.The cable is too long

B.A faulty transceiver

C.MTU mismatch

D.The interface is oversubscribed

AnswerB

Faulty optics can cause input errors.

Why this answer

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

Exam trap

The trap here is that candidates often confuse input errors with output drops or oversubscription, but input errors are strictly Layer 1 physical-layer issues, not congestion or configuration mismatches.

How to eliminate wrong answers

Option A is wrong because a cable that is too long would likely cause both input and output errors due to signal attenuation and timing issues, not exclusively input errors. Option C is wrong because an MTU mismatch typically causes packet drops at the IP layer (often seen as 'giants' or 'fragmentation needed' counters) and would not manifest as a high number of input errors on the physical interface; it would more likely cause output errors or discards. Option D is wrong because an oversubscribed interface would show output drops or congestion-related discards, not input errors; input errors are physical-layer issues, not capacity-related.

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75

Multi-Selectmedium

Which TWO methods can be used to restore a previous configuration on a Juniper device? (Select two.)

Select 2 answers

A.load override /config/rescue.conf

B.commit confirmed

C.rollback 1

D.load replace previous

E.rollback 0

AnswersA, C

Loads the rescue configuration, which is a backup.

Why this answer

Option A is correct because the 'load override /config/rescue.conf' command replaces the entire candidate configuration with the contents of the rescue configuration file, effectively restoring a previously saved baseline configuration. The rescue configuration is a special, manually saved configuration that persists across reboots and can be used to recover from configuration errors.

Exam trap

The trap here is that candidates often confuse 'rollback 0' with restoring a previous configuration, not realizing that rollback 0 refers to the current active configuration, while rollback 1 or higher is needed to access a prior committed configuration.

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