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Juniper® Routers Hardware and Features-3 Juniper® Routers Applications

Juniper Systems® and Cisco® Routers - A beginner's Guide

1. B. Junos® Networking Software:
  1. Command Line Interface (CLI)
    1. Operational Mode
    2. Configuration Mode
  2. Router Interface Configuration
    1. Interface Types
    2. Interface Configuration Syntax
    3. Examples of Router Interface Configuration
  3. RIP configuration using Junos®

1. B. The following paragraphs discuss the features of JUNOS CLI with a few configuration examples. The purpose is to provide the reader with an overall idea of JUNOS, and its configuration.

1. Command Line Interface (CLI)

The operating system software that powers the Juniper routers is called JUNOS™. The software is modular and standards based. Another important feature of JUNOS™ is that the software is platform independent (within Juniper hardware systems, not to be confused with other vendor hardware), thus delivering the same scalability and security across several hardware platforms.

JUNOS CLI is a simple to use, text-based command interface. We give various commands on CLI for configuring, troubleshooting and monitoring the software.

JINOS primarily supports two types of command modes.

a) Operational Mode

b) Configuration Mode

a) Operational Mode:

When we log in to the router and the CLI starts, we are at the top level of the CLI operational mode. In this mode, we enter the commands for

1. Controlling the CLI environment, and

2. Monitor and troubleshoot network connectivity, and

3. Initiating the Configuration Mode.

Frequently used commands in this mode include ping, show, traceroute, configure, etc.

b) Configuration Mode:

We use the Configuration mode for configuring the JUNOS software by creating a hierarchy of configuration statements. We enter the configuration mode by using the command “configure” as shown below:

user@host> configure

entering configuration mode



Issuing the commands one at a time using CLI can configure a JUNOS™ router or alternately, we can configure by creating a text (ASCII) file that contains the statement hierarchy. Remember to activate the configuration by using the command “commit” on the router.

As shown in the above example, the generic configuration prompt is user@host#. Ofcourse, we can change the prompt tby using appropriate command.

Statement Hierarchy:

We use the above configuration mode commands to create a statement hierarchy, and then configure the JUNOS software. The term “statement hierarchy” is used to define the sequence of commands used for configuring a particular feature (or features) of the router. An example statement hierarchy is given below:

user@host> configure

entering configuration mode

[edit] ----Top level

user@host#edit protocols ospf

[edit protocols ospf] ----protocols ospf hierarchy level


“set” commands are used to configure specific leaf statements.

Ex.: user@host# set hello-interval 14

2. Router Interface Configuration:

a. Types of Interfaces

Juniper Networks platform has primarily two types of interface. These are:

  1. Permanent interfaces, these are always present in the router and
  2. Transient interfaces, these can be inserted or removed from the router by user.

1. Permanent Interfaces: 

Each router has two permanent interfaces. These are:

a. Management Ethernet interface: This interface enables us to access the router using ssh, and telnet. The interface uses out-of-band connectivity, and does not provide packet forwarding capabilities for the transit data packets.

b. Internal Ethernet interface: Connects the Routing Engine (running the JUNOS Internet software) to the Packet Forwarding Engine. The router uses this interface as the main communications link between the JUNOS software and the components of the Packet Forwarding Engine. The Internal Ethernet interface is configured automatically when the JUNOS software boots.

2. Transient Interfaces:

Transient Interfaces are the interfaces that receive user’s data packets from the network and transmit the packets to the network. These interfaces are physically located on a Physical Interface Card. They can be inserted and removed at any time.

These interface need to be configured before using it. We can also configure the interfaces that are not in the chassis. When the JUNOS software activates the router’s configuration it finds out the interfaces that are present and activates only those interfaces.

In addition, each router has two serial ports, labeled console and auxiliary. Console port can be used to connect tty-type terminals to the router. The auxiliary port can connect to a modem.

b. Interface Representation and Command Syntax:

Using JUNOS software, a typical interface configuration will have the following syntax:


media_type: is the one that uniquely identifies the type of physical interface. It is a two-character word.

fpc: is the physical slot number in the chassis where the interface is located.

Pic: is the slot number on the FPC where the interface is located.

port: is the location on the PIC where the interface port (to which the interface is connected) is located.

unit: is the logical portion of the interface that is being configured.

Note: Some Physical interfaces use channel numbers instead if unit numbers. These numbers are represented using colon instead of period like media_type-fpc/pic/port:channel Number

C. Examples of Router Interface Configuration:

Following are some of the examples that configure the JUNOS software using CLI. Note that these are provided only to give a broad idea, and not necessarily accurate.

Example 1: Configuring a hostname on a router.



user@host#edit system

[edit system]

user@host#set host-name juniper

[edit system]


Example 2: Assigning an IP Address to a router interface.



user@host#edit interfaces so-0/0/0

[edit interfaces so-0/0/0]

user@host# edit unit 0

[edit interfaces so-0/0/0 unit 0]

user@juniper#edit family inet

[edit interfaces so-0/0/0 unit 0 family inet]

user@juniper#set address

[edit interfaces so-0/0/0 unit 0 family inet]


3. RIP Configuration using JUNOS.



user@host#edit protocols

[edit protocols]

user@host#edit rip

[edit protocols rip]

user@host#edit group neighbors

[edit protocols rip group neighbors]

user@host#set neighbor so-0/0/0.0;

[edit protocols rip group neighbors]

user@host#set neighbor so-0/0/1.0;

[edit protocols rip group neighbors]


Further, configuring for RIP involves creation and application of import/export policies. The same are not in the scope of this tutorial and not included here.

Juniper® Routers Hardware and Features-3 Juniper® Routers Applications
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