Junos OS Fundamentals

An engineer suspects that a recent software upgrade caused a compatibility issue. Which command should be used to revert the Junos OS to the previous version?

Which THREE actions can be performed in operational mode on a Junos device?

A network administrator needs to remove all configuration changes made since the last commit without affecting the current active configuration. Which command should be used?

A network administrator is configuring a new interface and wants to ensure that the interface is enabled and can pass traffic. Which configuration element is required?

A technician notices that the /var partition on a Junos device is 95% full. Which action will immediately free up disk space without affecting device operation?

Refer to the exhibit. An administrator wants to ensure that log messages are stored even if the remote syslog server becomes unavailable. What additional configuration is required?

Refer to the exhibit. The network administrator made a change that caused connectivity loss. They need to revert to the configuration before the most recent commit. Which command would accomplish this?

An engineer notices that a Juniper device is not saving configuration changes across reboots. What is the most likely cause?

A junior engineer is troubleshooting connectivity issues and wants to trace the path packets take to a remote destination. Which Junos command should be used?

What is the primary function of the fxp0 interface on a Juniper device?

Which THREE commands are valid in Junos operational mode? (Choose three.)

Which TWO statements are correct regarding the Junos OS configuration hierarchy?

Refer to the exhibit. A security analyst sees repeated login failures from 10.0.0.2 for user1. Which Junos feature can be used to automatically block further login attempts from that IP?

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

Which TWO commands are used to install and remove software packages on a Junos device?

A network administrator makes several changes to the configuration but decides to discard all uncommitted changes and start fresh. Which command should be used to revert the candidate configuration back to the current active configuration?

You are a network engineer at a company that operates a pair of Juniper SRX firewalls in an active/passive cluster (Chassis Cluster). The cluster has been running Junos 15.1X49-D100 for over a year. Management has mandated an upgrade to a newer version to address security vulnerabilities. You follow the recommended upgrade procedure and successfully upgrade the primary node (node0) first, then failover to make node0 the backup, and upgrade the new primary (node1). After the upgrade, both nodes have the same version and appear to be in the cluster, but you notice that the backup node (node0) is stuck in 'ineligible' state and does not synchronize configuration changes. What is the most likely cause?

An engineer wants to roll back to the previous configuration. Which command should be used?

An engineer wants to view the current active configuration file that the device is using. Which command displays this information?

An engineer needs to view the current active configuration on a Juniper device. Which command will display the configuration that is currently running?

Which TWO statements are true regarding Junos configuration groups?

An engineer needs to copy a configuration from one device to another. Which command should be used to export the current active configuration in a mergeable format?

Which Junos CLI mode allows a user to view the configuration and execute operational commands, but not make configuration changes?

A technician is troubleshooting a device that has an inconsistent configuration. They need to revert to the configuration that was committed exactly two commits ago. Which command sequence accomplishes this?

Which command saves the current operational state information to a file that can be provided to Juniper support for troubleshooting?

During a network traffic storm, a Juniper EX switch's CPU utilization spikes to 100%. Which command would best help identify the cause?

An administrator needs to quickly revert all uncommitted configuration changes and return the device to the last committed configuration. Which command accomplishes this?

A company wants to implement best practice for password recovery on Juniper devices to avoid service disruption. Which of the following is the recommended method?

Refer to the exhibit. Which log file will contain messages about authorization events?

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

Which THREE statements are true about commit operations in Junos OS?

Which TWO statements about the Junos OS configuration hierarchy are correct? (Choose two.)

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

Based on the exhibit, what is the most likely impact on the router?

An administrator notices that after committing a configuration change on a Juniper MX router, the device loses connectivity to the management network. The management interface is part of a dedicated management routing instance. Which of the following is the most likely cause?

Based on the exhibit, what is the most likely reason for the ping failure?

A network engineer is configuring a new Juniper MX router to replace an existing core router. The engineer has applied several configuration changes and wants to ensure that the new configuration can be tested safely. If the test fails (e.g., loss of management connectivity), the router should automatically revert to the previous configuration after a 5-minute period. The engineer performs a commit confirmed with a timeout of 5 minutes. After 4 minutes, the engineer verifies that the change is successful and wants to make it permanent. Which action should the engineer take to ensure the configuration persists?

You are administering a Juniper MX240 router that provides connectivity to multiple customer sites. The router uses BGP to exchange routes with two upstream ISPs. Recently, you applied a new firewall filter to the loopback interface to restrict management access. After committing the configuration, you can no longer establish SSH sessions to the router from the management network. You are currently connected via console. The loopback filter is still applied. You suspect the filter is blocking SSH traffic from the management network. What should you do to restore SSH access without losing the other filter rules?

A technician needs to upgrade the Junos OS on a device that is part of a redundant cluster. Which approach minimizes traffic disruption?

What is the purpose of the 'commit confirmed' command in Junos OS?

Refer to the exhibit. An operator tries to ping 192.168.1.2 from this router and fails. The router can ping itself (192.168.1.1). What is the most likely cause?

Refer to the exhibit. Which filesystem should the administrator investigate to free up disk space?

What happens when a user issues the 'request system reboot' command without any options?

You are a network administrator for a service provider that uses Juniper MX series routers to provide MPLS VPN services to customers. Management has requested that you implement a secure out-of-band management (OOBM) solution for all MX routers to ensure that management traffic is isolated from the production network, reducing the risk of unauthorized access and management plane attacks. You are tasked with designing the OOBM solution using a dedicated management interface (me0) and a separate management routing instance. Which of the following best practices should you follow?

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

An administrator is logged into a Juniper EX Series switch in configuration mode and wants to verify how the device will interpret a specific interface configuration before applying it. Which operational-mode command should the administrator use to validate the candidate configuration for syntax and semantic errors without committing it?

A network engineer made several configuration changes on a Juniper QFX switch to implement new VLANs. After committing the changes, the engineer realized that the new configuration caused a critical loss of connectivity to the management network. The engineer needs to revert to the previous configuration that was working. The switch is still accessible via the console port, and the engineer has privilege level access. The previous configuration was committed two commits ago, and the current active configuration is the problematic one. Which action should the engineer take to restore the previous working configuration?

A Junos device has multiple configuration files saved. Which command shows the available rollback configurations?

A Juniper device fails to boot and stops at the 'loader>' prompt. What is the most likely cause of this issue?

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

You are a network administrator for a large enterprise. You have a Juniper SRX firewall that is used as the primary internet gateway. Users are reporting that they are unable to access certain external websites. You check the device and find that the security policies appear correct, and the routing is in place. You suspect that the issue might be related to the DNS resolution. You want to verify that the device can resolve DNS names and that the DNS server configuration is correct. Which command should you use to test DNS resolution from the Juniper device?

What is the default behavior when a user logs in to a Junos device and enters configuration mode?

Your data center uses Juniper QFX5110 switches as leaf nodes in a Virtual Chassis Fabric (VCF) topology with QFX5100 as spine nodes. You are adding a new QFX5110 leaf node to the fabric. The new switch is physically connected to all spine nodes as per the cabling guidelines. However, after powering on the new switch, it does not automatically join the fabric. The existing fabric shows the new switch's member ID as 8, but it remains in 'standalone' state. The VCF has been operational for several months without issues. You check the configuration on the existing VC and notice that the 'virtual-chassis' configuration does not include the new member. What is the most likely reason the new switch does not join?

Refer to the exhibit. An administrator wants to see authentication-related logs like SSH logins. In the current configuration, which log file contains this information?

A network operator needs to backup the current configuration to a file on the local flash. Which command accomplishes this?

Your enterprise network uses Juniper EX4300 switches in a collapsed core design with RSTP (802.1w) as the Layer 2 loop prevention protocol. You add a new EX2300 switch to an access closet and connect it to two different core switches using two uplink interfaces configured in an LACP LAG. After connecting the new switch, you notice intermittent connectivity issues across the entire network, with some devices reporting temporary packet loss. The issue occurs sporadically, especially during configuration changes or when links flap. You suspect the problem is related to RSTP. Upon investigation, you see that the new switch's uplink interfaces are both in the forwarding state, but occasionally one of them transitions to blocking and then back to forwarding. What is the most likely cause of the intermittent issues?

Which command is used to view the terminal history of commands entered by the user?

Which THREE statements about the Junos OS file system are true? (Choose three.)

Which two statements correctly describe Junos OS login classes? (Choose two.)