Judy Estrin is a serial entrepreneur, having started seven tech companies since 1981. She was the former CTO of Cisco Systems from 1998-2000, and is on the boards of Disney and Packet Design and was a board member at Sun and FedEx for many years. She wrote Closing the Innovation Gap: Reigniting the Spark of Creativity in a Global Economy back in 2008. She now runs her own firm, JLabs, speaking and advising businesses on innovation, leadership and entrepreneurship.

I spoke to Estrin - someone who's career I've followed for decades -- this week about her life in startups and some of her favorite moments. Ironically, when I asked her what her favorite startup was, she said somewhat semi-seriously, "Raising my 21-year old son." She was not only acknowledging how important motherhood was to her but she was also trying to make a point that "women don't have to make a choice between parenting and work, and there are a lot of things you learn as a parent that apply to business leadership and vice-versa."

Nevertheless, she certainly has had numerous successes. Her first startup was Bridge Communications, an early networking company that she built to more than 400 people. She took it public and then eventually merged the company with 3Com. Precept Software, another of her startups, was bought by Cisco just prior to the company's stock price run-up, "so we had a great outcome for our investors."

Cisco was a completely different experience from her own startups, she said. "When I got to Cisco, I found myself a senior executive in someone else's organization. When I started they had 18,000 employees and double that when I left." It was also at the peak of the Internet bubble and she spent a lot of time working with various business units to think more long term and more synergistically.

One of the most difficult decisions Estrin had to make was at Network Computing Devices, when she chose to step down as CEO and had to help to find her own replacement. "I felt that I was approaching burn-out and needed a break. I learned how hard it is to find a good CEO and replace yourself. It is a lot easier to have someone else recruit and hire a CEO."

Estrin has hired numerous engineers over her career, but has found, to no surprise, that it is "harder to find technical women, especially in computer science. In this field, we don't connect the dots for kids growing up and give them a sense of how computer science makes a difference in the world. Engineers are often thought of being fields where people interact with machines and not people. There are other jobs for where computer science provides an important base, applying tech to solve very important problems that the world has, and involve collaboration and working with other people. We haven't done a really good job at exposing girls to what this part of computer science is all about."

Her best advice to women interested in a technical career is to first "Try it - take some classes, talk to people who work in tech, and don't assume it is boring or geeky or there aren't important problems to solve. Go for it, there are lots of opportunities. You need the right education foundation to prepare yourself for it. The basic computer science degree isn't just about learning a programming language but the algorithmic thinking to explain how to get a particular outcome and how you approach problem solving."

She certainly has seen computer science change quite a bit when she first started in the field many decades ago. "When I started my career it was about building computers for computers' sake." Now she says, it is all about the applications and how computers can be used in various parts of society.

Estrin is somewhat down on the venture community. "There is too much investment in incremental innovation, and not enough in building companies to solve important problems." But she is high on recent graduates: "There are many more kids coming out of school wanting to be entrepreneurs than in the past."

She has some advice to those budding entrepreneurs too: "If you don't have a great idea that you are passionate about and is big enough to take you where you need to go, you aren't going to get anywhere with your venture. The best entrepreneurial endeavors start with a problem that needs to be solved and that they are passionate about. Figure out unmet needs and filter through all your ideas and identify disruptive or new ways to address those needs that is the hardest part. Then you have to communicate your passion and build a team and get the execution down."

Read our our coverage of women entrepreneurs.