"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.
However, SDN will cut into the use of CLI for more routine tasks, Mimms said. Network engineers who know only CLI will end up like manual laborers whose jobs are replaced by automation. It's likely that some network jobs will be eliminated, he said.
This isn't the first time an alternative has risen up to challenge the CLI, said Walter Miron, a director of technology strategy at Canadian service provider Telus. There have been graphical user interfaces to manage networks for years, he said, though they haven't always had a warm welcome. "Engineers will always gravitate toward a CLI when it's available," Miron said.
Even networking startups need to offer a Cisco CLI so their customers' engineers will know how to manage their products, said Carl Moberg, vice president of technology at Tail-F Systems. Since 2005, Tail-F has been one of the companies going up against the prevailing order.
It started by introducing ConfD, a graphical tool for configuring network devices, which Cisco and other major vendors included with their gear, according to Moberg. Later the company added NCS (Network Control System), a software platform for managing the network as a whole. To maintain interoperability, NCS has interfaces to Cisco's CLI and other vendors' management systems.
CLIs have their roots in the very foundations of the Internet, according to Moberg. The approach of the Internet Engineering Task Force, which oversees IP (Internet Protocol) has always been to find pragmatic solutions to defined problems, he said. This detailed-oriented "bottom up" orientation was different from the way cellular networks were designed. The 3GPP, which developed the GSM standard used by most cell carriers, crafted its entire architecture at once, he said.
The IETF's approach lent itself to manual, device-by-device administration, Moberg said. But as networks got more complex, that technique ran into limitations. Changes to networks are now more frequent and complex, so there's more room for human error and the cost of mistakes is higher, he said.