Cisco’s senior executive team is looking a little sparse. David Ulevitch, who has been working in an advisory role with the company since May but prior to that headed up the firm's security business, announced he’s leaving to join venture capital firm Andreessen Horowitz.

Cisco announced earlier this year that Ulevitch was moving to an advisory role and working closely with David Goeckeler, executive vice president and general manager of Cisco's networking and security business. Gee Rittenhouse took over Ulevitch's role and was named senior vice president of engineering and security.

Nevertheless, Ulevitch is the third top Cisco executive to leave since August. He joins Hilton Romanski, who announced his departure in September. Romanski was Cisco’s SVP and chief strategy officer. He left to become a partner and senior managing director at Siris Capital. And in August, Yvette Kanouff, who served as SVP and GM of Cisco’s Service Provider Business, left the company.

Ulevitch was the founder of hybrid cloud security firm OpenDNS, which Cisco acquired in 2015 for $635 million. He was promoted to SVP of the security business in December 2016.

Martin Casado, another general partner at Andreessen Horowitz, announced Ulevitch’s move to the VC firm in a blog post. Casado was the co-founder and CTO of Nicira, which was acquired by VMware in 2012.

Cisco’s security business was the recent star of its fiscal fourth quarter earnings. During that quarter the security business reported $627 million in revenues, an increase of 12 percent year over year.