JNCIA-JUNOS Practice Test 30 — 15 Questions

Question 1

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?

Accepted Answer

The remote host is not reachable or is not responding to ARP requests.. The router can ping its own interface (192.168.1.1), confirming that the interface is up and IP is configured correctly. The failure to ping 192.168.1.2 indicates that the router cannot reach the remote host, most likely because the host is down, not connected, or not responding to ARP requests. ARP resolution is required for the router to map the destination IP to a MAC address on the local subnet; without a successful ARP reply, the router cannot send the echo request.

Answer

Reverse path forwarding (RPF) check is dropping the echo request.

Answer

The interface is administratively down.

Answer

Proxy ARP is not configured on the interface.

Question 2

Which TWO statements are true about the Junos file system? (Choose two.)

Accepted Answer

The /config directory contains configuration files.. Option A is correct because the /config directory in the Junos file system stores the active and backup configuration files, including juniper.conf and juniper.conf.gz. These files are critical for device operation and are loaded during the boot process.

Answer

The /altroot directory is a backup root filesystem.

Answer

The /kernel directory contains the operating system kernel.

Answer

The root directory (/) is a RAM disk.

Question 3

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?

Accepted Answer

rollback 2 followed by commit. Option B is correct because the `rollback 2` command reverts the candidate configuration to the state it was in two commits ago, but the change is not applied until a `commit` is issued. This two-step sequence (rollback followed by commit) is required to make the reverted configuration active. Without the commit, the device continues running the current active configuration.

Answer

rollback 2

Answer

commit confirmed 2

Answer

rollback 3

Question 4

An organization plans to upgrade Junos from version 18.1R3 to 19.1R1. The device currently runs on 18.1R3. Which statement is true regarding the upgrade process?

Accepted Answer

The device should be upgraded incrementally through each maintenance release before reaching 19.1R1.. Option B is correct because Junos OS requires an incremental upgrade path when the target release is more than one major version ahead. Since 18.1R3 and 19.1R1 are separated by a major version boundary, the device must first be upgraded to an intermediate release (e.g., 18.2 or 18.4) before applying the 19.1R1 image. Skipping major versions can cause incompatibilities in the file system or configuration database.

Answer

The upgrade can be performed directly from 18.1R3 to 19.1R1 using a single junos-install package.

Answer

The command 'request system software add' is used to install the new image.

Answer

The device will remain operational during the upgrade process without a reboot.

Question 5

A user needs to access the operational mode on a Junos device. What is the default prompt in operational mode?

Accepted Answer

user@host>. In Junos OS, the default prompt in operational mode is `user@host>`. The `>` character indicates that the device is ready to accept operational commands, such as `show` or `ping`, which do not alter the configuration. This is a fundamental distinction in Junos, where operational mode is for monitoring and troubleshooting, while configuration mode uses the `#` prompt.

Answer

user@host$

Answer

user@host%

Answer

user@host#

Question 6

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

Accepted Answer

request support information. The 'request support information' command collects a comprehensive snapshot of the current operational state, including configuration, logs, routing tables, and interface statistics, and packages it into a file (e.g., /var/tmp/support-info-date-time.tgz) that can be directly provided to Juniper support for troubleshooting. This is the standard Junos method for gathering diagnostic data.

Answer

monitor traffic

Answer

show system information

Answer

file copy

Question 7

An administrator wants to ensure that if a network interface fails, the routing protocol process automatically restarts. Which Junos feature should be configured?

Accepted Answer

auto-restart. Option A is correct because the 'auto-restart' feature in Junos automatically restarts the routing protocol process (e.g., rpd) if it detects that the interface associated with the protocol has failed. This ensures high availability by recovering the routing process without manual intervention, specifically targeting the scenario described in the question.

Answer

Nonstop Routing (NSR)

Answer

Bidirectional Forwarding Detection (BFD)

Answer

Graceful Restart

Question 8

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?

Accepted Answer

Apply a firewall filter to the loopback interface that polices SSH traffic.. Option D is correct because applying a firewall filter to the loopback interface (lo0) that polices SSH traffic can automatically block further login attempts from a specific IP address, such as 10.0.0.2. The loopback interface is the termination point for all control-plane traffic on a Junos device, including SSH sessions. By configuring a firewall filter with a policer that limits the rate of SSH packets from a source IP, excessive login failures can trigger the policer to drop subsequent packets, effectively blocking the attacker without manual intervention.

Answer

Configure SSH to accept only public key authentication for user1.

Answer

Disable the user1 account.

Answer

Set the 'session-limit' for user1 to prevent multiple login attempts.

Question 9

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?

Accepted Answer

interactive-commands. Option B is correct because the 'interactive-commands' log file is specifically designed to capture user-executed commands, including authentication-related events such as SSH login attempts and command execution. In Junos, this log is enabled by default and records all interactive CLI commands, which includes the authentication phase of SSH sessions.

Answer

utmp

Answer

security

Answer

messages

Question 10

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?

Accepted Answer

The routing instance for the management interface was accidentally removed. The management interface is part of a dedicated management routing instance (often named mgmt_junos). If this routing instance is accidentally removed during a commit, the management interface loses its routing context and becomes unreachable, causing loss of connectivity to the management network. This is a common misconfiguration when an administrator modifies routing instance configurations without realizing the management interface depends on it.

Answer

A firewall filter was applied to the management interface that blocks all traffic

Answer

NTP was configured with an incorrect server address

Answer

A syslog server was configured that is unreachable

Question 11

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

Accepted Answer

Configuration is organized in a hierarchical structure with levels. Option C is correct because the Junos OS configuration is organized in a hierarchical structure, resembling a tree with defined levels (e.g., [edit interfaces], [edit protocols ospf]). This hierarchy allows for logical grouping of configuration statements, making it easier to manage and navigate. The structure is enforced by the Junos CLI and the configuration database, which uses a set-based model rather than a flat file.

Answer

All configuration is stored in a flat file with line numbers

Answer

The hierarchy is stored in multiple configuration files that are merged at boot

Answer

Configuration values are inherited from the root level automatically

Question 12

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

Accepted Answer

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

Answer

commit check

Answer

commit synchronize

Answer

commit at 03:00

Question 13

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?

Accepted Answer

Create a dedicated routing instance for management, assign me0 to it, and apply a firewall filter to restrict access. Option D is correct because it follows Juniper's best practice for OOBM: creating a dedicated management routing instance (e.g., mgmt_junos) and assigning the me0 interface to it. This ensures management traffic is completely isolated from the production routing table (inet.0), preventing management plane attacks and unauthorized access. Applying a firewall filter on the me0 interface further restricts access to only authorized management hosts, aligning with security hardening guidelines.

Answer

Place me0 in the inet.0 routing table and rely on static routes

Answer

Enable VLAN tagging on me0 to separate management traffic into different subnets

Answer

Configure the me0 interface in the default routing instance with a simple ACL

Question 14

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?

Accepted Answer

The new switch does not have the same virtual-chassis ID configured as the existing fabric. In a Virtual Chassis Fabric (VCF), all member switches must share the same virtual-chassis ID to be recognized as part of the same fabric. The existing fabric has a configured virtual-chassis ID, but the new QFX5110, by default, has a different or no virtual-chassis ID set. Without a matching virtual-chassis ID, the new switch cannot join the fabric and remains in 'standalone' state, even though it is physically connected and assigned a member ID.

Answer

The new switch is running a different version of Junos that is not compatible with the fabric

Answer

The new switch is only connected to one spine node, and VCF requires full mesh connections to all spines

Answer

The new switch has 'set virtual-chassis no-split-detection' enabled, preventing it from joining

Question 15

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?

Accepted Answer

Boot into single-user mode and run file system checks.. The amber blinking LED and file system errors indicate a corrupted file system, which is common on factory-default devices if the flash memory was not properly initialized. Booting into single-user mode (option A) allows the administrator to run 'fsck' (file system check) to repair the root file system without loading the full Junos OS, which is the standard recovery procedure for such boot failures.

Answer

Perform a password recovery procedure to gain access.

Answer

Use the 'request system software add' command from the boot loader.

Answer

Reinstall the Junos OS using a USB flash drive with the software image.

JNCIA-JUNOS Practice Test 30 — 15 Questions

Exhibit

JNCIA-JUNOS Practice Test 30 — 15 Questions

Exhibit