When John Chambers ran Cisco Systems, acquisitions were one of his favorite ways to grow the company. By his own estimate, Cisco did 180 deals in his time there. But as he said in an interview with The Information this week, Cisco executives expected that one third would not succeed.

 It was a surprising admission for a former CEO, given how frequently investors complain about overpriced or badly executed mergers across industries. Mr. Chambers, though, believes that kind of failure rate is nothing to be ashamed of. Acquisitions are a “portfolio play like venture capital,” he said. To be successful, he said, acquisitive companies have to know how to take risk and accept outsiders into their ranks. Cisco’s notable misses included buying Scientific Atlanta for $6.9 billion in 2005 and selling the business for $600 million in 2015, and its $600 million purchase of video camera maker Flip in 2009. It shut down Flip two years later.