After serving as one of Silicon Valley’s most influential chief executives for more than two decades, John Chambers will step down as CEO of Cisco Systems in July.

The company announced today that Chambers will move into the role of executive chairman. He will be replaced by Chuck Robbins, 17-year veteran of the company who is currently Cisco’s senior vice president of operations.

“Today’s pace of change is exponential,” Chambers said in a statement. “Every company, city and country is becoming digital, navigating disruptive markets, and Cisco’s role in the digital transformation has never been more important. Our next CEO needs to thrive in a highly dynamic environment, to be capable of accelerating what is working very well for Cisco, and disrupting what needs to change.”

Chambers had previously said he wanted to step down as CEO by 2016. But the announcement today put an official date on the succession, and it also served as a moment to begin considering Chambers’ impact and his place in Silicon Valley’s history.

His time at the helm coincided with the rise of the Internet era in the mid-1990s. Chambers took charge of a company with less than 3,000 employees. The company was one of many emerging networking equipment companies.

But thanks to savvy leadership by Chambers, Cisco outflanked nearly every major rival in the late 1990s and saw its revenues and stock soar amid the dot-com bubble era. Chambers became the poster child of an era where CEOs of tech firms were elevated to rock-star status. Today, the company has more than 70,000 employees.

It was during the late 1990s that Chambers and Cisco became even more aggressive acquirers of startups, gaining a reputation for their ability to buy and integrate new companies and technologies quickly. For entrepreneurs and venture capitalists, Cisco for many years was one of the most desirable options to achieve the kind of exits necessary to continue expanding the Silicon Valley startup economy. During Chambers’ tenure, Cisco has bought 168 companies.

The dot-com crash forced Chambers and Cisco to retrench for several years, but the company has continued to navigate an evolving tech landscape, even if its stock has remained relatively flat for the past few years.

In recent years, Chambers became an outspoken proponent for the concept of the Internet of Things, which he believed would transform every industry around the planet. Along the way, Chambers also gained some notoriety for his support of Republican politicians such as President George Bush.

This summer, Robbins will take over a company that still has numerous challenges ahead as it seeks to attain leadership in network security and grapple with a challenging global economy.

Above: Cisco’s stock under Chambers’ 20-year tenure.