Cisco Systems Inc (CSCO.O) said on Monday that Chief Executive John Chambers would step down after 20 years at the helm to become executive chairman, and that 17-year company veteran Chuck Robbins would become CEO effective July 26.

Chambers, one of the longest-serving CEOs of a Silicon Valley company, will continue to be Cisco's chairman, the company said on Monday.

Cisco shares were down 0.5 percent at $28.97 in premarket trading.

Robbins, who became a board member on May 1, joined Cisco in 1997 and has been senior vice president of worldwide operations, leading the company's global sales and partner team.

Chambers, 65, has grown the network equipment maker's sales to about $48 billion from $1.2 billion since he took the top job in 1995.

He will now work with customers and governments around the world and focus on leading Cisco's role in country digitization, Cisco said.