I85PREP
⌘ K
JNCIE-ENT study materials
JNCIE-ENT study resources

JNCIE-ENT practice questions

One question at a time. Build your JNCIE-ENT understanding.

First 50 of 200 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

Continue in the practice tool above to load more questions, 50 at a time.

Question 1System Management and Monitoring

On a Junos device, which command displays the commit history for the candidate configuration, including the user and time of each commit?

  1. show configuration history
  2. show system rollback
  3. show system commit Correct answer.
  4. show configuration | compare rollback 1

Explanation

The show system commit operational command lists each commit recorded in the commit history, including the sequence number, the user who committed, the date and time, and any commit comment. It is the standard way to audit recent configuration changes on a Junos device.

Question 2System Management and Monitoring

Which Junos feature lets you automatically revert to the previous committed configuration if you do not confirm the new commit within a specified time?

  1. commit confirmed Correct answer.
  2. commit synchronize
  3. commit check
  4. commit full

Explanation

The commit confirmed command applies the candidate configuration but schedules an automatic rollback unless you issue a confirming commit within the timeout (10 minutes by default). It protects against locking yourself out with a remote change.

Question 3System Management and Monitoring

You want to see only the configuration statements that differ between the candidate configuration and the currently active configuration. Which command accomplishes this in configuration mode?

  1. show | display inheritance
  2. show system commit
  3. show configuration | display set
  4. show | compare rollback 0 Correct answer.

Explanation

In configuration mode, show | compare rollback 0 displays the differences between the candidate configuration and the active committed configuration (rollback 0). Lines prefixed with + are additions and lines prefixed with - are removals.

Question 4System Management and Monitoring

Which statement about Junos configuration groups is correct?

  1. Groups must be applied explicitly with the apply-groups statement at the hierarchy where they should take effect. Correct answer.
  2. Groups override all locally configured statements regardless of inheritance order.
  3. Groups apply only to interfaces configured under the [edit interfaces] hierarchy.
  4. Groups can contain only firewall filter definitions.

Explanation

Configuration groups hold reusable statements, and the apply-groups statement determines where those statements are inherited into the configuration. Statements configured locally at the same hierarchy normally take precedence over inherited group values.

Question 5System Management and Monitoring

Which configuration statement preserves the current active configuration as the rescue configuration?

  1. commit and-quit rescue
  2. request system configuration rescue save Correct answer.
  3. save rescue-configuration
  4. request system snapshot rescue

Explanation

The request system configuration rescue save command stores the current committed configuration as the rescue configuration, which can later be restored with request system configuration rescue rollback. This provides a known-good baseline for recovery.

Question 6System Management and Monitoring

A commit fails with the error 'commit check failed'. Which action best helps you identify the specific configuration problem?

  1. Issue commit full to bypass validation.
  2. Reboot the Routing Engine to clear the candidate configuration.
  3. Delete the rollback files with request system storage cleanup.
  4. Run commit check and review the error output, then use show | compare to inspect recent changes. Correct answer.

Explanation

commit check validates the candidate configuration and reports the hierarchy and reason for any failure. Reviewing that output together with show | compare helps isolate the offending statement before retrying the commit.

Question 7System Management and Monitoring

Which command shows the current Routing Engine CPU utilization on a Junos device?

  1. show system uptime
  2. show chassis routing-engine Correct answer.
  3. show system processes extensive
  4. show chassis environment

Explanation

show chassis routing-engine reports status for each Routing Engine, including CPU utilization, memory utilization, temperature, and uptime. It is the standard command for checking RE health and load.

Question 8System Management and Monitoring

Which syslog configuration statement on Junos sends messages of severity error and higher to a remote host?

  1. host 192.0.2.10 { any info; }
  2. console { any emergency; }
  3. host 192.0.2.10 { any error; } Correct answer.
  4. file messages { any error; }

Explanation

Under [edit system syslog], a host stanza with the facility any and severity error forwards messages at error severity and above (more severe) to the remote syslog server. Lower-severity messages such as warning and notice are excluded.

Question 9System Management and Monitoring

Which Junos logging facility should be configured to capture messages generated by the routing protocol process specifically?

  1. Any facility with the pfe keyword
  2. Any facility with the firewalls keyword
  3. The interactive-commands facility only
  4. The file or host target with the facility any and a matching severity Correct answer.

Explanation

Junos syslog targets specify a facility (such as any, firewall, pfe, or interactive-commands) plus a severity. Using facility any with the desired severity captures routing protocol messages along with other process messages.

Question 10System Management and Monitoring

Which command displays real-time log messages from the messages log file as they are generated?

  1. monitor start messages Correct answer.
  2. show log messages | match error
  3. clear log messages
  4. show log messages | last 10

Explanation

monitor start messages streams new entries from the messages log to the terminal in real time. You stop monitoring with monitor stop. It is useful for watching events during troubleshooting.

Question 11System Management and Monitoring

Which command displays the ARP table entries learned on a Junos device?

  1. show arp no-resolve Correct answer.
  2. show route forwarding-table
  3. show ethernet-switching table
  4. show interfaces extensive

Explanation

show arp no-resolve displays ARP entries without attempting to resolve unresolved addresses through DNS. It lists IP-to-MAC mappings learned on the device's interfaces.

Question 12System Management and Monitoring

Which command provides a summary of all configured interfaces with their administrative and link status?

  1. show interfaces terse Correct answer.
  2. show chassis hardware
  3. show configuration interfaces
  4. show interfaces extensive

Explanation

show interfaces terse gives a compact, one-line-per-interface summary including admin status (up/down) and link status. It is commonly used to confirm that interfaces are enabled and physically up.

Question 13System Management and Monitoring

Which Junos command verifies that the Routing Engine can reach a specific next-hop IP address using the routing table?

  1. ping 192.0.2.1
  2. show route 192.0.2.1 Correct answer.
  3. show arp 192.0.2.1
  4. traceroute 192.0.2.1

Explanation

show route 192.0.2.1 displays the best route and next-hop information for that destination, confirming how the routing table will forward traffic toward the address. It does not send probe packets.

Question 14System Management and Monitoring

Which command captures packet data on a Junos device for later analysis with tools such as Wireshark?

  1. clear interfaces statistics ge-0/0/0
  2. show log messages | match ge-0/0/0
  3. show interfaces ge-0/0/0 statistics
  4. monitor traffic interface ge-0/0/0 no-resolve Correct answer.

Explanation

monitor traffic interface ge-0/0/0 captures packets on the specified interface and displays them in tcpdump-like format; the no-resolve option prevents DNS lookups. Output can be saved to a file for later analysis.

Question 15System Management and Monitoring

Which command displays the current status of the Routing Engine redundancy state on a dual-RE chassis?

  1. show system redundancy status Correct answer.
  2. show chassis cluster status
  3. show chassis routing-engine
  4. show chassis redundancy

Explanation

show system redundancy status reports the mastership and backup state of the Routing Engines and whether graceful switchover is enabled. It is the standard command for verifying RE failover readiness.

Question 16System Management and Monitoring

You want to verify that a graceful Routing Engine switchover will occur without dropping traffic. Which condition must be met?

  1. The backup RE must have a different Junos version to provide rollback capability.
  2. The master RE must have GRES disabled.
  3. The backup RE must have the same Junos version and a synchronized configuration. Correct answer.
  4. The backup RE must be configured as the primary RE.

Explanation

Graceful RE switchover (GRES) requires the backup Routing Engine to run the same Junos release and to have a synchronized configuration so it can take over forwarding state seamlessly. Mismatched software or unsynchronized configuration prevents a graceful switchover.

Question 17System Management and Monitoring

Which command displays the packet forwarding statistics for a specific firewall filter term?

  1. show firewall log
  2. show policer
  3. show firewall filter <filter-name> Correct answer.
  4. show interfaces filter

Explanation

show firewall filter <filter-name> displays per-term counters for the named filter, showing how many packets and bytes matched each term. This confirms whether traffic is hitting the intended term.

Question 18System Management and Monitoring

Which command shows the current NTP synchronization status and association state on a Junos device?

  1. show ntp associations Correct answer.
  2. show ntp status
  3. show ntp servers
  4. show system time

Explanation

show ntp associations displays the configured NTP servers, their reachability, stratum, and synchronization state, indicating whether the device is synchronized to an upstream source.

Question 19System Management and Monitoring

Which command displays the system's current time zone and clock settings?

  1. show system uptime Correct answer.
  2. show configuration system time-zone
  3. show system time
  4. show ntp status

Explanation

show system uptime reports the current time, time zone, uptime, and load averages, which confirms the clock settings in effect. The configured time zone is set under [edit system time-zone].

Question 20System Management and Monitoring

Which command displays the current alarms and their severity on a Junos device?

  1. show log messages | match alarm
  2. show chassis alarms Correct answer.
  3. show system alarms
  4. show chassis environment

Explanation

show chassis alarms lists active chassis alarms such as fan failure, temperature, or power supply issues, along with their severity (major or minor). It is a first check when a device reports a hardware problem.

Question 21System Management and Monitoring

Which command shows the amount of memory and CPU used by individual processes on a Junos device?

  1. show system storage
  2. show system processes extensive Correct answer.
  3. show chassis routing-engine
  4. show system statistics

Explanation

show system processes extensive lists running processes with their CPU and memory usage, sorted by CPU. It helps identify a process consuming excessive resources.

Question 22System Management and Monitoring

A Junos device is dropping traffic because a firewall filter policer is exceeding its rate. Which command displays policer statistics?

  1. show interfaces policer
  2. show class-of-service policer
  3. show policer Correct answer.
  4. show firewall

Explanation

show policer displays statistics for configured policers, including the number of packets and bytes that were conforming and non-conforming. This confirms whether the policer is discarding traffic.

Question 23System Management and Monitoring

Which command generates a core dump file for a specific Junos process to help diagnose a crash?

  1. show system core-dumps
  2. request system generate-core
  3. request system core-dumps Correct answer.
  4. request system process core-dump

Explanation

The request system core-dumps command manages core dump files, allowing you to list, save, or delete them for analysis. Core dumps capture process memory at the time of a crash and are useful for vendor diagnostics.

Question 24System Management and Monitoring

Which command displays the version of Junos running on the device along with hardware model information?

  1. show configuration version
  2. show system uptime
  3. show version Correct answer.
  4. show chassis hardware

Explanation

show version reports the Junos software release, the hardware model, and the uptime of the device. It is the primary command for confirming the running software version.

Question 25System Management and Monitoring

Which command saves the current configuration to a file on the device in configuration mode?

  1. copy running-config /var/tmp/config-backup.conf
  2. commit save /var/tmp/config-backup.conf
  3. archive configuration /var/tmp/config-backup.conf
  4. save /var/tmp/config-backup.conf Correct answer.

Explanation

In configuration mode, the save command writes the current candidate configuration to a specified file path. The file can later be loaded with the load command for restoration or comparison.

Question 26System Management and Monitoring

Which Junos configuration statement enables a device to send SNMP traps to a management station at 192.0.2.10 using SNMPv2c?

  1. set snmp trap-group NMS targets 192.0.2.10 Correct answer.
  2. set snmp interface 192.0.2.10
  3. set snmp community public clients 192.0.2.10
  4. set snmp view all oid .1 include

Explanation

Traps are delivered to defined destinations through a trap-group whose targets list the receiving management station addresses. The community statement only authenticates and optionally restricts request sources; it does not define trap destinations. A trap-group must also be bound to a community for the traps to be sent.

Question 27System Management and Monitoring

You want Junos to archive configuration files automatically each time a commit succeeds, keeping the ten most recent versions on the local disk. Which configuration accomplishes this?

  1. set system auto-snapshot
  2. set system configuration-database commit-history
  3. set system commit synchronize
  4. set system archival configuration transfer-on-commit Correct answer.

Explanation

The archival configuration hierarchy with transfer-on-commit causes a copy of the committed configuration to be saved each time a commit succeeds. Archive sites and maximum retained copies are defined under archive-sites and transfer-interval options. Commit synchronize only mirrors commits between Routing Engines and does not retain versioned copies.

Question 28System Management and Monitoring

A Junos device must authenticate login users against a RADIUS server at 198.51.100.5 while still allowing a local fallback account. Which configuration is required?

  1. set system authentication-order radius Correct answer.
  2. set system root-authentication encrypted-password "$6$..."
  3. set system login class superuser permissions all
  4. set system radius-server 198.51.100.5 secret junos

Explanation

The authentication-order statement determines which authentication methods are tried and in what sequence. Listing radius first with password as a later method allows the device to fall back to locally configured accounts when the server is unreachable. The radius-server statement alone defines the server but does not change the order in which methods are consulted.

Question 29System Management and Monitoring

Which command displays the configured login classes and the permissions granted to each class?

  1. show system login classes detail
  2. show configuration system login class Correct answer.
  3. show cli authorization
  4. show system users

Explanation

Login classes and their allow/deny permission sets live under the [edit system login class] hierarchy, so the configuration view is the authoritative display. Operational commands show active users or the permissions of the current session, not the full class definitions. Reviewing the configuration is the reliable way to audit what each class permits.

Question 30System Management and Monitoring

An operator needs to confirm which configuration groups are applied to the current configuration and whether a group is inactive. Which command best serves this purpose?

  1. show system commit
  2. show configuration groups
  3. show system rollback 0
  4. show configuration | display inheritance Correct answer.

Explanation

Piping the configuration through display inheritance expands group and interface-range applications, showing the effective statements each group contributes. It also marks inherited values so you can see where they originate. Simply listing groups does not reveal whether they are applied or inactive.

Question 31System Management and Monitoring

Which command displays the last several commits along with the user and method used for each?

  1. show system commit Correct answer.
  2. show system uptime
  3. show configuration | compare rollback 1
  4. show log messages | match commit

Explanation

The show system commit command lists recent commits with timestamps, the user who performed them, and the method (CLI, Junos OS load, or rollback). It is the standard way to audit configuration change history on a device. Log matching may show commit events but does not present the structured commit history.

Question 32System Management and Monitoring

You need to schedule a one-time commit of the candidate configuration for 02:00 tomorrow and require that the commit be rolled back automatically if connectivity is lost. Which feature should you configure?

  1. commit comment
  2. commit and-quit
  3. commit at with commit confirmed Correct answer.
  4. commit synchronize

Explanation

The commit at statement schedules a commit at a future time, and combining it with commit confirmed causes an automatic rollback unless the commit is confirmed within the confirmation window. This protects against a scheduled change that severs management access. Commit synchronize and commit comment do not provide scheduling or automatic rollback.

Question 33System Management and Monitoring

Which command displays the current contents of the candidate configuration without committing it?

  1. show configuration | compare
  2. show system rollback 0
  3. show | display set
  4. show configuration Correct answer.

Explanation

In configuration mode, show configuration displays the candidate configuration as currently edited. Adding the pipe to display set renders it in set-command form, but the base command shows the candidate. Commands like compare and rollback operate on differences or saved versions rather than showing the working candidate.

Question 34System Management and Monitoring

A commit fails because a referenced prefix-list is not defined. Which approach most directly isolates the offending statement?

  1. Increase the commit timeout value
  2. Run commit check and read the reported error line and hierarchy Correct answer.
  3. Disable commit synchronization
  4. Reload the factory default configuration

Explanation

Commit check validates the candidate and reports the specific hierarchy and statement that fails validation, which points directly at the undefined reference. Adjusting timeouts or synchronization does not address a semantic validation error. Reloading defaults would discard the intended configuration rather than diagnose it.

Question 35System Management and Monitoring

Which command shows the rescue configuration currently stored on the device?

  1. show configuration | compare rollback 49
  2. show system rollback 0
  3. show system rescue configuration Correct answer.
  4. show system commit

Explanation

The rescue configuration is a saved known-good configuration that can be restored with rollback rescue. The show system rescue configuration command displays its stored contents so you can verify what would be restored. Rollback comparisons and commit history do not specifically display the rescue copy.

Question 36System Management and Monitoring

You need to verify that a Junos device is generating flow records and exporting them to a collector at 203.0.113.20 on UDP port 2055. Which command confirms the export destination and active flows?

  1. show services accounting flow inline-jflow Correct answer.
  2. show services flow-collector statistics
  3. show services flow-monitoring version9 template
  4. show services flow-monitoring interface

Explanation

The show services accounting flow command displays flow accounting status, including the configured export destination and port along with active flow counts. It confirms both that flows are being accounted and where records are sent. Template and collector commands relate to other flow components and do not confirm active flow export.

Question 37System Management and Monitoring

Which command displays the status of configured RPM probes, including probe type and last probe results, on a Junos device?

  1. show services rpm active-servers
  2. show services rpm probe-test
  3. show services rpm probe-results Correct answer.
  4. show services rpm history-results

Explanation

RPM probes are configured under [edit services rpm] and their results are displayed with show services rpm probe-results, which reports probe type, target, and latest round-trip measurements. This is the standard operational view for verifying synthetic probe health. Other command forms do not report probe results.

Question 38System Management and Monitoring

A device must send syslog messages to a remote collector using TCP so that delivery is reliable. Which statement accomplishes this?

  1. set system syslog file messages any any
  2. set system syslog host 203.0.113.5 any any transport tcp Correct answer.
  3. set system syslog host 203.0.113.5 any any
  4. set system syslog host 203.0.113.5 any any port 514

Explanation

The transport tcp option under the syslog host statement causes messages to be delivered over TCP rather than the default UDP. This provides reliable, ordered delivery to the collector. Specifying a port or facility/severity alone does not change the transport protocol.

Question 39System Management and Monitoring

Which command displays the current status of configured traceoptions, including the log file and flag settings?

  1. show log <filename> | last Correct answer.
  2. show system processes extensive
  3. show configuration system syslog
  4. show log messages

Explanation

Traceoption output is written to a log file named in the traceoptions configuration, and viewing that file with show log <filename> reveals current trace activity. This confirms which events are being captured. Syslog configuration and process listings do not show trace output.

Question 40System Management and Monitoring

You want to confirm that the device is receiving valid time from an NTP server and that the stratum and offset are acceptable. Which command output provides the stratum and offset for each association?

  1. show ntp associations Correct answer.
  2. show ntp status
  3. show ntp servers
  4. show system uptime

Explanation

Show ntp associations lists each configured server or peer with its stratum, reachability, and offset, allowing you to judge synchronization quality. The status command reports whether the local clock is synchronized but not per-association details. Uptime and server listings do not report stratum and offset per association.

Question 41Layer 2 Switching and Features

On a Junos EX Series switch, a trunk interface carries traffic for VLANs 10, 20, and 30. Which configuration element causes the switch to transmit frames for VLAN 20 untagged toward the attached device?

  1. Removing VLAN 20 from the trunk member list
  2. Configuring the interface as an access interface with VLAN 20
  3. Enabling storm control on the trunk interface
  4. Assigning VLAN 20 as the native VLAN on the trunk interface Correct answer.

Explanation

On Junos, frames belonging to the native VLAN on a trunk port are sent untagged, while all other member VLANs are tagged with 802.1Q headers. The native VLAN is set with the native-vlan-id statement under the interface. Setting a VLAN as native therefore makes its traffic untagged toward the peer.

Question 42Layer 2 Switching and Features

You want an EX switch port to dynamically join VLANs based on the source MAC address of incoming frames. Which feature should you configure?

  1. 802.1X authenticated VLAN assignment
  2. MAC RADIUS authentication Correct answer.
  3. Voice VLAN with LLDP-MED
  4. Static MAC-to-VLAN binding

Explanation

MAC RADIUS authentication uses the source MAC address as the credential, and the RADIUS server returns VLAN attributes that place the port in a dynamic VLAN. This differs from 802.1X, which uses EAP identities rather than MAC addresses. Static bindings are not dynamic, and voice VLAN uses LLDP-MED advertisement.

Question 43Layer 2 Switching and Features

A Junos EX switch is configured with a Virtual Chassis of four members. Which statement accurately describes how the Virtual Chassis control plane operates?

  1. Only the master runs the control plane while line cards on all members forward using the master's configuration Correct answer.
  2. The backup member forwards traffic but never receives configuration from the master
  3. All members run active routing engines and load-share control plane processing
  4. Each member runs an independent routing engine and they synchronize via VRRP

Explanation

In a Junos Virtual Chassis, one member is elected master and runs the single control plane; the other members act as line cards that forward traffic using the master's configuration. The backup member maintains a synchronized copy of the configuration for failover but does not forward independently as a routing engine.

Question 44Layer 2 Switching and Features

Which spanning-tree protocol variant does Junos support that builds a single topology per VLAN and interoperates with Cisco PVST+?

  1. VSTP Correct answer.
  2. STP (802.1D)
  3. RSTP
  4. MSTP

Explanation

VSTP (VLAN Spanning Tree Protocol) runs a separate spanning-tree instance per VLAN on Junos and is designed to interoperate with Cisco PVST+. MSTP maps multiple VLANs to shared instances rather than one instance per VLAN, and RSTP/STP are single-instance protocols.

Question 45Layer 2 Switching and Features

You need to protect an access port from a loop caused by a user connecting a small unmanaged switch. Which Junos feature disables the port when it receives BPDUs?

  1. Root guard
  2. Loop protection
  3. Edge port filtering
  4. BPDU guard Correct answer.

Explanation

BPDU guard disables a port configured as an edge (access) port if it receives a BPDU, preventing user devices from participating in spanning tree. Root guard instead prevents a port from becoming the root port. Loop protection detects loops differently and does not key on BPDU reception.

Question 46Layer 2 Switching and Features

A Layer 2 network uses MSTP. Two switches disagree on the MSTP region configuration. What is the most likely consequence?

  1. The switches form a single region and share the CIST
  2. The switches refuse to form a spanning tree and all ports enter blocking
  3. The switches automatically negotiate a common region name
  4. Each switch treats the other as being in a different region, and the CIST root is elected across regions Correct answer.

Explanation

MSTP regions are defined by matching region name, revision level, and VLAN-to-instance mapping. If these differ, the switches belong to different regions, and the common internal spanning tree (CIST) is computed between regions rather than sharing a single region topology.

Question 47Layer 2 Switching and Features

Which Junos statement on an EX switch enables a trunk interface to accept frames tagged with VLAN IDs that are not configured on the switch?

  1. Enable VLAN translation on the interface
  2. Set the interface to access mode
  3. Enable flexible-vlan-tagging and configure the interface as trunk Correct answer.
  4. Configure the interface as a trunk member of all VLANs

Explanation

Flexible VLAN tagging allows an interface to accept both tagged and untagged frames, and combined with trunk mode it permits tagged frames for VLANs not explicitly configured. Access mode accepts only untagged frames, and VLAN translation rewrites tags rather than admitting unknown VLANs.

Question 48Layer 2 Switching and Features

You configure a routed VLAN interface (RVI) for VLAN 100 on an EX switch. Which statement about the RVI is correct?

  1. The RVI forwards frames between VLANs without any additional configuration
  2. The RVI is automatically assigned to all trunk interfaces
  3. The RVI provides Layer 3 termination for VLAN 100 and requires an IP address to route Correct answer.
  4. The RVI disables Layer 2 switching for VLAN 100

Explanation

An RVI (irb interface in Junos) provides Layer 3 termination for a VLAN and needs an IP address to participate in routing. It does not automatically forward between VLANs without routing configuration, and it does not disable Layer 2 switching for the VLAN.

Question 49Layer 2 Switching and Features

Which Junos feature allows a single physical interface to carry multiple logical units, each mapped to a different VLAN, without using 802.1Q tagging on the wire?

  1. VLAN translation
  2. Flexible VLAN tagging
  3. Logical interface per VLAN with no tagging (multiple untagged logical units) Correct answer.
  4. Q-in-Q tunneling

Explanation

Junos allows multiple logical units on one physical interface, each associated with a VLAN, but only one logical unit can be untagged; additional units require tagging. Strictly, multiple untagged logical units on one physical interface are not supported, so the premise of untagged multi-VLAN on one interface is invalid. Among the options, the closest supported construct is logical units per VLAN, but tagging is required for more than one.

Question 50Layer 2 Switching and Features

Which statement best describes the purpose of the Junos `interface-mac-limit` statement on an access port?

  1. It limits the number of IP addresses assigned to the interface
  2. It limits the number of MAC addresses learned on the interface to mitigate MAC flooding Correct answer.
  3. It limits the number of BPDUs accepted per second
  4. It limits the number of VLANs allowed on the interface

Explanation

The interface-mac-limit statement caps how many source MAC addresses can be learned on a port, protecting the MAC table from being flooded. When the limit is exceeded, the configured action (such as drop or shutdown) is taken. It does not govern VLAN counts, BPDUs, or IP addresses.