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Configuration Basics: Key Knowledge Areas for JNCIA-Junos JN0-105 Exam

June 29,2024

Successfully passing the Junos, Associate (JNCIA-Junos) JN0-105 exam requires a solid understanding of Configuration Basics. This article aims to help candidates master this critical topic by providing a detailed overview of the essential elements for configuring Junos devices. We will cover each key component and provide practical examples and explanations to enhance your knowledge. Additionally, Passcert collected JNCIA-Junos JN0-105 practice questions with detailed explanations will help you solidify your understanding and prepare effectively for the exam.

Configuration Basics

1. Factory-Default State

Definition: The factory-default state is the original configuration of the device when it is shipped. It includes the minimal configuration necessary to bring up the system.

Command: request system zeroize (resets the device to its factory-default state by removing all configuration files, log files, and other system data).

2. Initial Configuration

Steps: Includes setting the root password, hostname, and basic interface settings.

Commands:

configure (enters configuration mode)

set system root-authentication plain-text-password (sets the root password)

set system host-name <hostname> (sets the device hostname)

set interfaces <interface> unit 0 family inet address <IP-address> (configures an interface)

3. User Accounts

Commands:

set system login user <username> class <class> authentication plain-text-password (creates a user with a specified login class)

set system login user <username> full-name "<full name>" (adds a full name to the user account)

4. Login Classes

Definition: Login classes define user permissions and access privileges.

Commands:

set system login class <class-name> permissions <permissions> (defines permissions for a login class)

set system login user <username> class <class-name> (assigns a login class to a user)

5. User Authentication Methods

Methods: Include local password, SSH keys, RADIUS, and TACACS+.

Commands:

set system authentication-order [password radius tacplus] (sets the order of authentication methods)

6. Interface Types and Properties

Types: Ethernet, SONET/SDH, T1/E1, etc.

Commands:

set interfaces <interface> description "<description>" (adds a description to an interface)

set interfaces <interface> unit 0 family inet address <IP-address> (configures the IP address for an interface)

7. Configuration Groups

Definition: Configuration groups allow you to apply common configurations to multiple parts of the system.

Commands:

set groups <group-name> <configuration> (creates a configuration group)

set apply-groups <group-name> (applies a configuration group)

8. Additional Initial Configuration Elements

NTP: set system ntp server <NTP-server>

SNMP: set snmp community <community-name> authorization read-only

System Log: set system syslog file <filename> any <log-level>

9. Configuration Archival

Commands:

set system archival configuration transfer-on-commit (enables configuration archival on commit)

set system archival configuration archive-sites <URL> (defines where to archive configurations)

10. Logging and Tracing

Commands:

set system syslog file <filename> any <log-level> (sets logging levels)

set system traceoptions flag all (enables tracing options)

11. Rescue Configuration

Definition: A known good configuration that can be loaded in case of configuration errors.

Command: request system configuration rescue save (saves the current configuration as the rescue configuration)

JNCIA-Junos JN0-105 Practice Questions with Explanations

Real-time Usage Statistics for Busiest Interfaces

You are asked to view the real-time usage statistics for the busiest interfaces on a device running Junos OS. Which command will achieve this task?

A. monitor traffic absolute-sequence

B. monitor interface traffic

C. monitor traffic

D. show interfaces extensive

Answer: B

Explanation: The monitor interface traffic command is used to display real-time statistics for traffic on interfaces.

Device that Uses Destination IP to Forward Packets

Which type of device uses the destination IP address to forward packets?

A. Layer 3 router

B. Layer 2 switch

C. repeater

D. hub

Answer: A

Explanation: A Layer 3 router uses the destination IP address in the packet header to make forwarding decisions.

Routing Tables and Forwarding Tables

When considering routing tables and forwarding tables, which two statements are correct? (Choose two.)

A. The routing table is used by the RE to select the best route.

B. The forwarding table stores all routes and prefixes from all protocols.

C. The forwarding table is used by the RE to select the best route.

D. The routing table stores all routes and prefixes from all protocols.

Answer: A and D

Explanation: The routing table is used by the Routing Engine (RE) to select the best route and stores all routes and prefixes learned from various protocols.

Request System Configuration Rescue Save Command

What will the request system configuration rescue save command do?

A. It saves the most recently committed configuration as the rescue configuration.

B. It saves the candidate configuration as the rescue configuration.

C. It saves a configuration version prior to the configuration most recently committed as the rescue configuration.

D. It activates the rescue configuration.

Answer: A

Explanation: This command saves the current, active configuration as the rescue configuration.

Addresses in Ethernet Frame Header

Which two addresses are included in an Ethernet frame header? (Choose two.)

A. source IP address

B. source MAC address

C. destination IP address

D. destination MAC address

Answer: B and D

Explanation: An Ethernet frame header contains the source and destination MAC addresses.

Components in a Transport Header

Which two components are included in a transport header? (Choose two.)

A. destination port number

B. source MAC address

C. source port number

D. destination MAC address

Answer: A and C

Explanation: The transport header (TCP/UDP) includes the source and destination port numbers.

Advantages of Using Junos OS

What are two advantages of using the Junos OS? (Choose two.)

A. It enables you to roll back to a previous configuration.

B. It pushes your configuration changes "live" immediately.

C. It is modular.

D. It supports up to a maximum of two previous configurations.

Answer: A and C

Explanation: Junos OS allows you to roll back to previous configurations and has a modular architecture.

Protocol for Learning IPv4 Neighbor's MAC Address

Which protocol is responsible for learning an IPv4 neighbor's MAC address?

A. Address Resolution Protocol (ARP)

B. Network Address Translation (NAT)

C. Media Access Control Security (MACsec)

D. Neighbor Discovery Protocol (NDP)

Answer: A

Explanation: ARP is used to map IPv4 addresses to MAC addresses.

Junos OS Component for Maintaining Forwarding Table

Which Junos OS component is responsible for maintaining the forwarding table?

A. Routing Engine

B. chassis control daemon

C. Packet Forwarding Engine

D. management daemon

Answer: C

Explanation: The Packet Forwarding Engine (PFE) maintains the forwarding table and forwards packets based on its entries.

By understanding these configuration basics and practicing with the provided questions, you will be well-equipped to tackle the JNCIA-Junos exam. This guide not only helps you grasp the fundamental concepts but also prepares you to apply your knowledge effectively, ensuring a smoother and more confident exam experience.

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