Navigating the Junos CLI: Tips and Tricks

Juniper Networks' Junos OS stands tall among the leading networking operating systems, known for its stability, modularity, and comprehensive features. One of the first touchpoints for many engineers working with Junos is its Command-Line Interface (CLI). This post aims to equip you with insightful tips and tricks to master the Junos CLI, ensuring efficiency and precision in your network operations.

Junos CLI: A Brief Overview

The Junos CLI is a text-based interface that allows administrators to configure, manage, and troubleshoot Juniper devices. With its hierarchical structure, it offers a systematic approach to device configuration and monitoring.

Essential Junos CLI Commands

Before diving into tips and tricks, let's familiarize ourselves with some foundational commands:

• show: Used to display configurations and operational information.
• set: Employed to define configurations.
• delete: Removes specific configurations.
• commit: Applies changes made to the active configuration.

Now, onto the tips and tricks!

1. Command Autocompletion and Help

Save time by letting the CLI assist you. Type a portion of a command and hit the Tab key:

user@router# set inter[Tab]

This will autocomplete the command if there’s a unique match or provide available options.

The ? key serves as your inbuilt CLI guide, listing available commands at any hierarchy level.

2. Configuration Navigation with Anchors

When deep within the configuration hierarchy, use the ^ (caret) followed by the level you wish to navigate:

user@router# edit interfaces ge-0/0/0
[edit interfaces ge-0/0/0]
user@router# ^interfaces
[edit interfaces]

3. Reviewing Uncommitted Changes

Use the show | compare command to view changes against the active configuration. This is particularly useful before committing changes.

4. Rolling Back Configurations

Made an error? Junos maintains a snapshot of previous configurations. Use rollback followed by the desired configuration number:

user@router# rollback 1

5. Annotate Your Commits

Documentation is crucial. When committing changes, add annotations:

user@router# commit comment "Updated ge-0/0/0 IP address."

This creates a record of changes, aiding in troubleshooting and audits.

6. Operational Mode Shortcuts

While in operational mode, if you wish to view a configuration without entering the configuration mode, use show configuration:

user@router> show configuration interfaces ge-0/0/0

7. Filtering Outputs

The CLI provides tools to filter output, making data extraction efficient:

• match: Displays lines containing a specific keyword.
• except: Excludes lines containing a specific keyword.

Example:

user@router> show interfaces | match "ge-0/0/0"

8. Operational Commands from Configuration Mode

Need to run an operational command while in configuration mode? Prefix it with run:

[edit]
user@router# run show interfaces terse

9. Refreshing Your Knowledge with man

Similar to UNIX, Junos CLI offers man (manual) pages. For instance, to understand the show command better, use:

user@router> man show

Wrapping Up

The Junos CLI, with its robust set of tools and features, can appear daunting initially. However, with these tips and tricks under your belt, you'll be navigating it like a pro in no time. As you venture deeper into the world of Juniper and Junos, remember that practice, coupled with a keen understanding of the CLI's nuances, will serve as your best allies.

Stay engaged for more deep dives into Junos OS and its vast array of capabilities. Here's to efficient networking!