Shares of network security provider Fortinet Inc soared in their debut on the Nasdaq on Wednesday, in what is on track to be among the strongest debuts of any initial public offering in 2009, after pricing above the expected range.

Its shares were trading at $17.05, or 36.4 percent above the IPO price, in early trading, after having reached as high as $17.50.

Fortinet raised $156.5 million in its initial public offering on Tuesday after the stock flotation priced for $12.50, above expectations.

Silicon Valley-based Fortinet's products integrate firewalls, Web-filtering and spam-filtering.

Fortinet, whose shareholders include venture capital firms Redpoint Ventures and Meritech Capital, sold 12.5 million shares. Earlier in the week, the company had increased the size of the deal by 500,000 shares to meet strong demand.

Excluding Fortinet, so far this year there have been 10 venture capital-backed IPOs valued at a combined $1.4 billion. There were only six VC-backed IPOs in 2008, totaling $470.2 million, according to Thomson Reuters data.

Fortinet had sales of $181.4 million in the first nine months of 2009, up 18.8 percent over a year earlier, with a profit of $16.2 million.

The IPO's lead underwriters are Morgan Stanley, J.P. Morgan Securities & Co and Deutsche Bank Securities.

(Reporting by Clare Baldwin and Phil Wahba; Editing by Derek Caney)