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Will software-defined networking kill network engineers' beloved CLI?

Networks defined by software may require more coding than command lines, leading to changes on the job

By , IDG News Service
August 30, 2013 02:36 PM ET

IDG News Service - SDN (software-defined networking) promises some real benefits for people who use networks, but to the engineers who manage them, it may represent the end of an era.

Ever since Cisco made its first routers in the 1980s, most network engineers have relied on a CLI (command-line interface) to configure, manage and troubleshoot everything from small-office LANs to wide-area carrier networks. Cisco's isn't the only CLI, but on the strength of the company's domination of networking, it has become a de facto standard in the industry, closely emulated by other vendors.

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As such, it's been a ticket to career advancement for countless network experts, especially those certified as CCNAs (Cisco Certified Network Associates). Those network management experts, along with higher level CCIEs (Cisco Certified Internetwork Experts) and holders of other official Cisco credentials, make up a trained workforce of more than 2 million, according to the company.

A CLI is simply a way to interact with software by typing in lines of commands, as PC users did in the days of DOS. With the Cisco CLI and those that followed in its footsteps, engineers typically set up and manage networks by issuing commands to individual pieces of gear, such as routers and switches.

SDN, and the broader trend of network automation, uses a higher layer of software to control networks in a more abstract way. Whether through OpenFlow, Cisco's ONE (Open Network Environment) architecture, or other frameworks, the new systems separate the so-called control plane of the network from the forwarding plane, which is made up of the equipment that pushes packets. Engineers managing the network interact with applications, not ports.

"The network used to be programmed through what we call CLIs, or command-line interfaces. We're now changing that to create programmatic interfaces," Cisco Chief Strategy Officer Padmasree Warrior said at a press event earlier this year.

Will SDN spell doom for the tool that network engineers have used throughout their careers?

"If done properly, yes, it should kill the CLI. Which scares the living daylights out of the vast majority of CCIEs," Gartner analyst Joe Skorupa said. "Certainly all of those who define their worth in their job as around the fact that they understand the most obscure Cisco CLI commands for configuring some corner-case BGP4 (Border Gateway Protocol 4) parameter."

At some of the enterprises that Gartner talks to, the backlash from some network engineers has already begun, according to Skorupa.

"We're already seeing that group of CCIEs doing everything they can to try and prevent SDN from being deployed in their companies," Skorupa said. Some companies have deliberately left such employees out of their evaluations of SDN, he said.

Not everyone thinks the CLI's days are numbered. SDN doesn't go deep enough to analyze and fix every flaw in a network, said Alan Mimms, a senior architect at F5 Networks.

"It's not obsolete by any definition," Mimms said. He compared SDN to driving a car and CLI to getting under the hood and working on it. For example, for any given set of ACLs (access control lists) there are almost always problems for some applications that surface only after the ACLs have been configured and used, he said. A network engineer will still have to use CLI to diagnose and solve those problems.

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