Juniper Beginner

JN0-104

JNCIA-Junos (Juniper Networks Certified Associate - Junos)

The JNCIA-Junos (JN0-104) certification validates foundational knowledge of the Junos operating system and basic networking concepts. This entry-level certification is designed for networking professionals with beginner to intermediate knowledge of networking and Juniper Networks products. It serves as the foundation for all other Juniper certification tracks.

The exam covers five key areas: Networking Fundamentals (22%), Junos OS Fundamentals (23%), User Interfaces (23%), Junos Configuration Basics (18%), and Routing Fundamentals (14%). Candidates will need to understand networking basics including the OSI model, TCP/IP, Ethernet, and IPv4/IPv6, as well as Junos-specific concepts like the Junos architecture, CLI navigation, configuration modes, and basic routing protocols (static routes, RIP, OSPF basics).

This certification is ideal for network engineers, administrators, and support personnel who work with Juniper Networks devices. It demonstrates a basic understanding of Junos OS and provides the foundation for pursuing specialist and professional-level Juniper certifications. The JN0-104 exam was last updated in 2024.

Updated 2024 Networking

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JN0-104 Practice Exam 1

Comprehensive 50-question practice exam covering all five JNCIA-Junos domains: networking fundamentals, Junos OS fundamentals, user interfaces, Junos configuration basics, and routing fundamentals.

50 Q 90 минути 60%

Пробно караме

€5.00

JN0-104 Practice Exam 2

Second comprehensive 50-question practice exam covering all JNCIA-Junos domains: networking fundamentals, Junos OS fundamentals, user interfaces, Junos configuration basics, and routing fundamentals. This exam tests your readiness for the Juniper Networks Certified Associate certification.

50 Q 90 минути 60%

Пробно караме

€5.00

JN0-104 Practice Exam 3

Third comprehensive 50-question practice exam for the Juniper Networks JNCIA-Junos JN0-104 certification covering networking fundamentals, Junos OS fundamentals, user interfaces, Junos configuration basics, and routing fundamentals.

50 Q 90 минути 60%

Пробно караме

€5.00

JN0-104 Practice Exam 4

Comprehensive 50-question practice exam covering all five Juniper JNCIA-Junos domains: networking fundamentals, Junos OS fundamentals, user interfaces, Junos configuration basics, and routing fundamentals.

50 Q 90 минути 60%

Пробно караме

€5.00

JN0-104 Practice Exam 5

Comprehensive 50-question practice exam covering all five JNCIA-Junos domains: Networking Fundamentals, Junos OS Fundamentals, User Interfaces, Junos Configuration Basics, and Routing Fundamentals.

50 Q 90 минути 60%

Пробно караме

€5.00

JN0-104 Practice Exam 6

Comprehensive 50-question practice exam covering all five JNCIA-Junos domains: Networking Fundamentals, Junos OS Fundamentals, User Interfaces, Junos Configuration Basics, and Routing Fundamentals. Covers NAT concepts, control plane protection, CLI environment settings, secure configuration practices, and route leaking between routing instances.

50 Q 90 минути 60%

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JN0-104 Cheat Sheet

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JN0-104 JNCIA-Junos Exam Details

Detail	Value
Exam Code	JN0-104
Certification	JNCIA-Junos (Juniper Networks Certified Internet Associate)
Duration	90 minutes
Number of Questions	65 questions
Passing Score	60%
Question Format	Multiple choice, multiple select
Exam Fee	$200 USD
Prerequisite	None

Domain Weight Breakdown

Domain	Weight
Junos OS Fundamentals	30%
Networking Fundamentals	15%
Routing Fundamentals	25%
Switching & Security	30%

Juniper Certification Path

The JNCIA-Junos is Juniper Networks' entry-level certification that validates a candidate's understanding of Junos OS fundamentals, networking concepts, and basic routing and switching. It is the foundation for all Juniper certification tracks. After passing the JNCIA-Junos, candidates can advance to specialist-level certifications such as JNCIS-ENT (Enterprise Routing and Switching), JNCIS-SEC (Security), JNCIS-Cloud (Cloud), or JNCIS-MistAI (AI-Driven Enterprise).

The exam covers Junos OS architecture, CLI navigation, configuration basics, routing and switching fundamentals, and security concepts. Candidates should understand how Junos OS differs from other network operating systems, particularly its modular software architecture, candidate configuration model, and protocol daemon structure.

Junos OS Architecture

Junos OS is built on a FreeBSD kernel with a modular software architecture. Each major function runs as a separate process (daemon) in its own protected memory space. If one process fails, it does not affect other processes. This design ensures stability and high availability.

Component	Function
Routing Engine (RE)	Control plane: runs routing protocols, maintains routing tables, manages the device. Runs Junos OS software
Packet Forwarding Engine (PFE)	Data plane: forwards packets based on forwarding table received from RE. Hardware-based for performance
Kernel	FreeBSD-based microkernel handling process management, memory, and interprocess communication

Key Junos Daemons (Processes)

Daemon	Name	Function
rpd	Routing Protocol Daemon	Runs all routing protocols (OSPF, BGP, IS-IS, RIP), maintains routing table
mgd	Management Daemon	Handles CLI commands, configuration management, NETCONF/XML API
chassisd	Chassis Daemon	Manages chassis components, fans, power supplies, alarm conditions
dcd	Device Control Daemon	Controls physical interface properties (speed, duplex, MTU)
snmpd	SNMP Daemon	Handles SNMP requests and traps
pfed	PFE Daemon	Manages communication between RE and PFE

Junos CLI Modes

Mode	Prompt	Purpose
Operational Mode	user@router>	Monitor, troubleshoot, show commands, ping, traceroute
Configuration Mode	user@router#	Change device configuration, enter with `configure`
Shell (Unix)	user@router%	FreeBSD shell access, enter with `start shell`

Configuration Mode Types

Mode	Command	Behavior
Shared (default)	configure	Multiple users can edit simultaneously; last commit wins
Exclusive	configure exclusive	Locks configuration; no other user can edit until you exit
Private	configure private	Each user gets a private copy; changes merged at commit

Candidate Configuration & Commit Model

Junos uses a candidate configuration model. Changes are made to a candidate config and do not take effect until you issue the commit command. This allows reviewing changes before activation and rolling back if issues occur.

Command	Description
`commit`	Activate candidate configuration
`commit check`	Validate configuration without applying
`commit confirmed <minutes>`	Auto-rollback if not confirmed within time window
`commit at <time>`	Schedule commit for a specific time
`rollback 0-49`	Revert to a previous configuration (0 = current active, 1 = previous)
`show \| compare`	Show differences between candidate and active configuration
`show \| compare rollback N`	Compare candidate with rollback N

Tip: Junos stores up to 50 rollback configurations (rollback 0 through rollback 49). The commit confirmed command is essential for remote changes; if connectivity is lost, the device will automatically roll back.

Essential CLI Commands

Command	Mode	Description
`show route`	Operational	Display routing table
`show interfaces terse`	Operational	Brief interface status summary
`show configuration`	Operational	Show active (committed) configuration
`show system alarms`	Operational	Display active system alarms
`monitor traffic interface`	Operational	Live packet capture on an interface
`set / delete / deactivate`	Configuration	Add, remove, or disable configuration statements
`edit <hierarchy>`	Configuration	Navigate to a specific configuration hierarchy level
`top / up`	Configuration	Navigate to top or up one level in hierarchy

Interface Naming Convention

Junos interfaces follow the format: type-fpc/pic/port.unit. For example, ge-0/0/0.0 means Gigabit Ethernet, FPC slot 0, PIC slot 0, port 0, logical unit 0.

Interface Type	Prefix	Description
Fast Ethernet	fe-	100 Mbps Ethernet
Gigabit Ethernet	ge-	1 Gbps Ethernet
10-Gigabit Ethernet	xe-	10 Gbps Ethernet
100-Gigabit Ethernet	et-	100 Gbps Ethernet
Loopback	lo0	Virtual loopback interface
Management	fxp0 / em0 / me0	Out-of-band management interface
Aggregated Ethernet	ae	Link aggregation group (LAG)
VLAN Tagged	irb	Integrated Routing and Bridging (Layer 3 VLAN interface)

Junos Configuration Hierarchy

Junos configuration is organized in a tree hierarchy. Major top-level sections include:

system - Hostname, DNS, NTP, syslog, login, services (SSH, NETCONF)
interfaces - Physical and logical interface configuration
routing-options - Static routes, router ID, autonomous system
protocols - Routing protocols (OSPF, BGP, IS-IS, LLDP)
security - Zones, policies, NAT, IPsec (SRX platforms)
policy-options - Routing policies, prefix lists, community definitions
firewall - Stateless firewall filters (ACLs)
vlans - VLAN definitions for switching
class-of-service - QoS configuration

Junos Routing Tables

Junos maintains multiple routing tables for different purposes. The main unicast routing table is inet.0 for IPv4 and inet6.0 for IPv6.

Routing Table	Purpose
inet.0	IPv4 unicast routes
inet6.0	IPv6 unicast routes
inet.1	IPv4 multicast forwarding cache
inet.2	IPv4 unicast routes for multicast RPF checks
inet.3	MPLS path information (used by BGP)
mpls.0	MPLS label switching table
instance.inet.0	VRF routing instance tables

Route Preference (Administrative Distance)

Junos uses route preference (equivalent to administrative distance) to select the best route when multiple sources provide routes to the same destination. Lower preference values are preferred.

Route Source	Default Preference
Directly Connected	0
Local	0
Static	5
OSPF Internal	10
IS-IS Level 1 Internal	15
IS-IS Level 2 Internal	18
RIP	100
OSPF External	150
IS-IS Level 1 External	160
IS-IS Level 2 External	165
BGP (EBGP and IBGP)	170

Tip: Unlike Cisco, Junos uses the same default preference (170) for both EBGP and IBGP routes. Route selection between EBGP and IBGP is handled by the BGP path selection algorithm, not by preference.

Static Routing Configuration

# Static route with next-hop

set routing-options static route 10.0.0.0/24 next-hop 192.168.1.1

# Floating static route (higher preference = less preferred)

set routing-options static route 10.0.0.0/24 next-hop 192.168.2.1 preference 200

# Discard route (null route / black hole)

set routing-options static route 192.168.100.0/24 discard

# Default route

set routing-options static route 0.0.0.0/0 next-hop 10.0.0.1

# Static route with qualified next-hop (backup)

set routing-options static route 10.0.0.0/24 qualified-next-hop 192.168.3.1 preference 15

OSPF Configuration Basics

OSPF in Junos is configured under the protocols ospf hierarchy. Interfaces are added to areas, not networks. OSPF area 0 is the backbone area.

# Configure OSPF area 0 with interfaces

set protocols ospf area 0.0.0.0 interface ge-0/0/0.0

set protocols ospf area 0.0.0.0 interface lo0.0 passive

# Set router ID

set routing-options router-id 1.1.1.1

# Verify OSPF

show ospf neighbor

show ospf interface

show ospf database

show route protocol ospf

Routing Policy Framework

Junos routing policies control route advertisement and acceptance. Policies are defined under policy-options and applied using import and export statements within protocol configuration.

Term	Description
from	Match conditions (protocol, route-filter, prefix-list, community)
then	Actions (accept, reject, next-hop, local-preference, metric, community)
term	Named rule within a policy; evaluated in order

# Example routing policy

set policy-options policy-statement EXPORT-STATIC term 1 from protocol static

set policy-options policy-statement EXPORT-STATIC term 1 then accept

# Apply to OSPF export

set protocols ospf export EXPORT-STATIC

Route Resolution & Forwarding Table

The routing table (inet.0) maintained by the RE contains all learned routes. The active route (best route per destination) is installed into the forwarding table and pushed to the PFE. The forwarding table is what the PFE uses for actual packet forwarding.

show route - Shows the routing table with active routes marked with an asterisk (*)
show route forwarding-table - Shows the forwarding table on the PFE
show route <prefix> detail - Shows detailed route information including all learned paths

VLAN Configuration in Junos

Junos EX Series switches support VLANs using the vlans hierarchy. Interfaces are assigned to VLANs using interface-mode access or trunk.

# Create VLANs

set vlans SALES vlan-id 10

set vlans ENGINEERING vlan-id 20

# Access port configuration

set interfaces ge-0/0/1 unit 0 family ethernet-switching interface-mode access

set interfaces ge-0/0/1 unit 0 family ethernet-switching vlan members SALES

# Trunk port configuration

set interfaces ge-0/0/23 unit 0 family ethernet-switching interface-mode trunk

set interfaces ge-0/0/23 unit 0 family ethernet-switching vlan members [SALES ENGINEERING]

# Native VLAN on trunk

set interfaces ge-0/0/23 native-vlan-id 999

Spanning Tree Protocol (STP)

Junos supports STP, RSTP (default on EX Series), and MSTP. STP prevents Layer 2 loops by blocking redundant paths while maintaining a loop-free topology.

STP Version	Standard	Key Feature
STP	802.1D	Original; slow convergence (30-50 seconds)
RSTP	802.1w	Rapid convergence (1-2 seconds); Junos default
MSTP	802.1s	Multiple spanning trees mapped to VLAN groups
VSTP	Juniper proprietary	Per-VLAN STP (similar to Cisco PVST+)

# Configure RSTP with bridge priority

set protocols rstp bridge-priority 4096

set protocols rstp interface ge-0/0/0 edge

# Verify STP

show spanning-tree bridge

show spanning-tree interface

Link Aggregation (LAG / ae Interfaces)

# Enable aggregated Ethernet device count

set chassis aggregated-devices ethernet device-count 2

# Assign physical interfaces to ae bundle

set interfaces ge-0/0/0 ether-options 802.3ad ae0

set interfaces ge-0/0/1 ether-options 802.3ad ae0

# Configure ae0 with LACP

set interfaces ae0 aggregated-ether-options lacp active

set interfaces ae0 unit 0 family ethernet-switching interface-mode trunk

set interfaces ae0 unit 0 family ethernet-switching vlan members all

Security Zones (SRX Series)

On SRX firewalls, interfaces are assigned to security zones. Traffic between zones requires a security policy to permit it. By default, all inter-zone traffic is denied.

Zone	Typical Use
trust	Internal LAN (trusted network)
untrust	Internet-facing (untrusted network)
dmz	Demilitarized zone for public-facing servers

# Configure security zones

set security zones security-zone trust interfaces ge-0/0/1.0 host-inbound-traffic system-services all

set security zones security-zone untrust interfaces ge-0/0/0.0 host-inbound-traffic system-services dhcp

# Security policy: trust to untrust

set security policies from-zone trust to-zone untrust policy ALLOW-WEB match source-address any

set security policies from-zone trust to-zone untrust policy ALLOW-WEB match destination-address any

set security policies from-zone trust to-zone untrust policy ALLOW-WEB match application [junos-http junos-https]

set security policies from-zone trust to-zone untrust policy ALLOW-WEB then permit

Firewall Filters (Stateless ACLs)

Junos firewall filters are stateless packet filters applied to interfaces. They operate similarly to ACLs but use a term-based structure with match conditions and actions.

# Create firewall filter

set firewall family inet filter PROTECT-RE term ALLOW-SSH from protocol tcp

set firewall family inet filter PROTECT-RE term ALLOW-SSH from destination-port 22

set firewall family inet filter PROTECT-RE term ALLOW-SSH then accept

set firewall family inet filter PROTECT-RE term DENY-ALL then discard

# Apply filter to loopback (protect RE)

set interfaces lo0 unit 0 family inet filter input PROTECT-RE

Tip: Firewall filters are stateless (no session tracking). Security policies on SRX are stateful. For the exam, know the difference: firewall filters = stateless ACLs, security policies = stateful firewall rules.

NAT on SRX (Overview)

NAT Type	Description	Use Case
Source NAT	Translates source IP (outbound)	Internal hosts accessing the internet
Destination NAT	Translates destination IP (inbound)	Publishing internal servers to the internet
Static NAT	1:1 bidirectional mapping	Servers needing both inbound and outbound translation

User Authentication & System Services

# Configure local user

set system login user admin class super-user authentication plain-text-password

# Enable SSH access

set system services ssh

# Configure NTP

set system ntp server 10.0.0.1

# Configure syslog

set system syslog host 10.0.0.50 any info

set system syslog file messages any notice

Login Class	Permissions
super-user	Full access to all commands and configuration
operator	Clear, network, reset, trace, view permissions
read-only	View permissions only
unauthorized	No permissions

OSI Model & TCP/IP Stack

OSI Layer	Name	TCP/IP Layer	PDU	Key Protocols
7	Application	Application	Data	HTTP, HTTPS, DNS, DHCP, SNMP, SSH
6	Presentation		Data	SSL/TLS, JPEG, ASCII
5	Session		Data	NetBIOS, RPC
4	Transport	Transport	Segment	TCP (reliable), UDP (best-effort)
3	Network	Internet	Packet	IPv4, IPv6, ICMP, OSPF, BGP
2	Data Link	Network Access	Frame	Ethernet, 802.1Q, ARP, PPP
1	Physical	Network Access	Bits	Cables, fiber, wireless signals

IPv4 Subnetting Quick Reference

CIDR	Subnet Mask	Usable Hosts	Common Use
/30	255.255.255.252	2	Point-to-point links
/24	255.255.255.0	254	Standard LAN segment
/16	255.255.0.0	65,534	Large campus network
/32	255.255.255.255	1	Loopback / host route

IPv6 Fundamentals

Address Type	Prefix	Description
Global Unicast	2000::/3	Routable on the internet (like public IPv4)
Link-Local	fe80::/10	Auto-assigned, local link only (always present)
Unique Local	fc00::/7	Private addressing (like RFC 1918 in IPv4)
Multicast	ff00::/8	One-to-many communication
Loopback	::1	Self-reference address

IPv6 uses 128-bit addresses written in hexadecimal. Junos supports dual-stack (IPv4 + IPv6) by configuring both family inet and family inet6 on the same interface.

TCP vs UDP

Feature	TCP	UDP
Connection	Connection-oriented (3-way handshake)	Connectionless
Reliability	Guaranteed delivery (ACKs, retransmissions)	Best effort (no guarantees)
Ordering	Sequence numbers ensure ordering	No ordering
Speed	Slower (overhead)	Faster (minimal overhead)
Use Cases	HTTP, SSH, FTP, SMTP, BGP	DNS, DHCP, SNMP, VoIP, TFTP

DHCP & DNS Basics

DHCP (Dynamic Host Configuration Protocol): Automatically assigns IP addresses and configuration parameters to clients. DORA process: Discover (broadcast), Offer, Request, Acknowledge. Junos devices can act as DHCP server, client, or relay agent.

DNS (Domain Name System): Resolves hostnames to IP addresses. Uses UDP port 53 for queries (TCP 53 for zone transfers). Configure DNS on Junos: set system name-server 8.8.8.8.

Ethernet Frame & 802.1Q VLAN Tagging

Standard Ethernet frame: Preamble (8 bytes), Dest MAC (6), Source MAC (6), EtherType (2), Payload (46-1500), FCS (4). 802.1Q inserts a 4-byte VLAN tag between Source MAC and EtherType, containing the 12-bit VLAN ID (supporting VLANs 1-4094). This increases the maximum frame size from 1518 to 1522 bytes.

Tip: In Junos, native VLAN ID is configured per interface with native-vlan-id. Frames on the native VLAN are sent untagged on trunk ports.

Junos vs Cisco IOS: Terminology

Concept	Junos (Juniper)	IOS (Cisco)
Configuration Model	Candidate + Commit	Running config (immediate)
Config Rollback	rollback 0-49 (built-in)	config replace / archive
Route Preference	Route Preference (lower = better)	Administrative Distance
ACLs	Firewall Filters (stateless)	Access Control Lists
Interface VLAN	IRB (Integrated Routing and Bridging)	SVI (Switch Virtual Interface)
Trunk Encapsulation	802.1Q only	802.1Q and ISL (legacy)
OS Architecture	Modular (separate daemons)	Monolithic (single process in IOS)
Link Aggregation	ae interfaces	EtherChannel / Port-Channel

Routing Engine vs Packet Forwarding Engine

Aspect	Routing Engine (RE)	Packet Forwarding Engine (PFE)
Plane	Control Plane	Data Plane (Forwarding Plane)
Processing	Software-based (general-purpose CPU)	Hardware-based (ASICs)
Functions	Routing protocols, CLI, management, routing table	Packet forwarding, filtering, QoS, policers
Table	Routing table (inet.0)	Forwarding table (copied from RE)
Failure Impact	Device cannot learn new routes or be managed	Packets not forwarded

Security Policies vs Firewall Filters

Feature	Security Policies (SRX)	Firewall Filters
Type	Stateful	Stateless
Session Tracking	Yes (return traffic automatically allowed)	No (each direction needs separate rules)
Zone-Based	Yes (from-zone, to-zone)	No (applied per-interface)
Application Awareness	Yes (predefined and custom applications)	Limited (port/protocol only)
Platform	SRX Series only	All Junos platforms
Default Action	Deny all inter-zone traffic	Accept (implicit at end unless denied)

Junos Platform Families

Platform	Series	Primary Function
MX Series	Universal Routing	Service provider / enterprise edge routing, high performance
SRX Series	Services Gateway	Firewall, VPN, UTM, IDP (security)
EX Series	Ethernet Switching	Campus and data center Layer 2/3 switching
QFX Series	Data Center Switching	High-performance data center top-of-rack / spine switches
PTX Series	Packet Transport	Core / WAN transport routers
ACX Series	Universal Access	Metro / access / aggregation routers

OSPF Area Types

Area Type	LSA Types Allowed	External Routes
Normal	1, 2, 3, 4, 5	Full external route information
Stub	1, 2, 3	Default route from ABR replaces externals
Totally Stubby	1, 2	Only default route (no inter-area or external)
NSSA	1, 2, 3, 7	Type 7 LSAs (converted to Type 5 at ABR)

# Junos OSPF stub area

set protocols ospf area 0.0.0.1 stub

# NSSA area

set protocols ospf area 0.0.0.2 nssa

Junos Software Upgrade Methods

Method	Description
Standard Upgrade	`request system software add package.tgz` - standard upgrade with reboot
No-Validate	Add `no-validate` to skip compatibility checks (use with caution)
ISSU	In-Service Software Upgrade - upgrade with minimal downtime on dual RE systems
USB/Console	Boot from USB for disaster recovery

Tip: Always verify the current software version with show version and check available storage with show system storage before upgrading. Use request system snapshot to back up the current system before any upgrade.

JN0-104

JNCIA-Junos (Juniper Networks Certified Associate - Junos)

JN0-104 Practice Exam 1

JN0-104 Practice Exam 2

JN0-104 Practice Exam 3

JN0-104 Practice Exam 4

JN0-104 Practice Exam 5

JN0-104 Practice Exam 6

Отключете цялото съдържание за JN0-104

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Флаш карти

Налични езици

Теми на изпита

JN0-104 Cheat Sheet

JN0-104 JNCIA-Junos Exam Details

Domain Weight Breakdown

Juniper Certification Path

Junos OS Architecture

Key Junos Daemons (Processes)

Junos CLI Modes

Configuration Mode Types

Candidate Configuration & Commit Model

Essential CLI Commands

Interface Naming Convention

Junos Configuration Hierarchy

Junos Routing Tables

Route Preference (Administrative Distance)

Static Routing Configuration

OSPF Configuration Basics

Routing Policy Framework

Route Resolution & Forwarding Table

VLAN Configuration in Junos

Spanning Tree Protocol (STP)

Link Aggregation (LAG / ae Interfaces)

Security Zones (SRX Series)

Firewall Filters (Stateless ACLs)

NAT on SRX (Overview)

User Authentication & System Services

OSI Model & TCP/IP Stack

IPv4 Subnetting Quick Reference

IPv6 Fundamentals

TCP vs UDP

DHCP & DNS Basics

Ethernet Frame & 802.1Q VLAN Tagging

Junos vs Cisco IOS: Terminology

Routing Engine vs Packet Forwarding Engine

Security Policies vs Firewall Filters

Junos Platform Families

OSPF Area Types

Junos Software Upgrade Methods