The battle between JUNOS and IOS

Despite marketing claims, are Juniper and Cisco's operating systems really that different?


Cisco's 20+ year leadership position in routing has been challenged by Juniper over the past 10 years. Juniper has swiped about a quarter of Cisco's share of the service provider router market and is also coming after Cisco in the enterprise. Juniper credits its JUNOS operating system strategy for much of its success while criticizing Cisco's IOS software direction as fragmented. Here's a comparison of both OSes.

The Challenger

JUNOS is a modular operating system that provides a single code base across most of Juniper's platforms.


The JUNOS command line interface is intended to be friendly and easy to use for engineers steeped in years of IOS.

The Incumbent

Cisco's IOS is a monolithic operating system that's been in networks for over 20 years.

The IOS command hierarchy

A schematic diagram of some common IOS commands.

Monolithic vs. modular

Monolithic OSes -- like IOS -- tightly couple processes like file systems, procedure calls and device drivers, to the OS kernel; a modular system, like JUNOS, decouples them.

We want to hear from YOU!

Could the JUNOS vs. IOS be one of the great technology debates of our time? Read up and speak out here .