Cisco's John Chambers says he knows that one third of his acquisitions will fail

Cisco on Wednesday bought Portcullis Computer Security for an undisclosed sum, an 87-person security consulting company in the UK.

Executive chairman John Chambers noted that this was the company's 182nd acquisition, he said on stage to Box CEO Aaron Levie at Levie's Boxworks tech conference.

But, he warned, acquisitions are always a crap shoot.

"Remember, the majority of acquisitions in our industry fail, if you consider did you gain market share? Was it a good decision for your shareholders? Did you keep the technology people and get the next generation of products out?," Chambers said.

"I know 1/3 are going to fail. Chuck knows 1/3 are going to fail. If we knew which ones we wouldn't have done them," he said.

The biggest mistake?

Chambers is forever known for acquiring the Flip camera for $590 million back in 2009 and shutting it in 2011 after Apple put a camera in the iPhone phone.

But he told Levie that he doesn't consider Flip to be his worst failure.

"Flip is one we missed on. We didn't miss the trend, we missed focusing on the device, not on the cloud. By the way, it doesn't make our top 20 acquisitions in terms of cost," Chambers said.

Chambers said he's more upset, in retrospect, at how he missed the internet bubble.

"We clearly got surprised like the whole market did, in 2001," he said on stage.

Cisco was an internet bubble darling, it's stock trading at $77, a peak it has never come close to again.

But in the third fiscal quarter of 2001, after the bubble burst, Cisco's sales plunged 30 percent. Chambers wrote off $2.2 billion worth of inventory and laid off 8,500. In September, 2001, the stock was trading at just over $12.

Now that was painful, Chambers recalls. He remembers hearing from GE CEO Jack Welch around the time.

"Jack Welch called me up in the late 1990's, he said, 'John, you have a good company.' I said, 'what does it take to be great?' He said, 'a near-death experience.' I thought he was kidding. He called me up at 2001 and said, 'You now have a great company.' I said, 'Jack, it doesn't feel like it. I'm getting beat up in the press. The shareholders are all over me,'" Chambers remembers.

Then Welch told him, "You made the transitions you had to make to reposition the company for the future. Watch, you'll come back even stronger."

Cisco is now on track to generate $49 billion in revenues for its fiscal 2016, Chambers said, and it employs 70,0o0 employees. And Chambers said on stage that he "hired all but 23" of them.