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JunOS basics

First time login


When you login with “root” you will be in “shell mode” which is similar to linux.
You can switch to “operational mode” with the “cli” command.



It is not necessary to repeat these steps when you already have a user.

To switch to the last mode use the “configure” command:

Entering configuration mode




%  – shell mode
>  – operational mode
#  – configuration mode

Checking interfaces

Similarly to Cisco there are multiple options to gather information regarding the interfaces:

show interface terse
show interface brief
show interface 

In addition you get more information using the “detailed” or “extensive” keywords.

Checking configuration

show configuration

When you are in configuration mode, the “show” command displays a specific part of the configuration.
Example: #show interfaces ge-0/0
This command is equal with Cisco’s “show run int gi0/0”

You can put a comment into any part of the configuration with the “annotate” command.


Modifying the configuration

To modify any part of the configuration use the “edit” command and the name of the structure you that you would like to modify.
Example: #edit interfaces

root# edit interfaces

[edit interfaces]

Notice that the “edit” part in the brackets has been extended with “interfaces”.

If you want to do same real changes you must use the “set” command.
Example: #edit interfaces em0 unit 0 family inet

In case you would like to go back to another section you can use the “up” command which will take you one level back. You can also add a number to specify how many levels would you like to go back: up 2
Or you can use “top” to go back to the top of the configuration.


Unlike Cisco, Juniper has quite advanced help system. You have multiple options to get more information regarding JunOS or a simple protocol:

help topic – Gives some detailed descriptions in context of a particular topic.
help reference – Gives more information regarding the command structure.
help apropos – Helps to find a command that relates to a topic.


>help topic interfaces address
>help reference interfaces address

#This command will list all of the commands that have some relevance with "snooping"
>help apropos snooping



Juniper – Architecture


  • EX Series Ethernet Switches (13.2 Tbps)


  • E Series Broadband Services Routers
  • T Series Core Routers (25 Tbps)
  • M Series Multiservice Edge Routers (320 Gbps)
  • MX Series 3D Universal Edge Routers (80 Tbps)


  • SRX Series (200 Gbps)

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