What: Shares of Infoblox (NYSE:BLOX), a provider of network control solutions, slumped on Friday despite the company reporting fiscal-fourth-quarter results that beat analyst estimates. At 12:40 p.m. Friday, the stock was down about 10%.

So what: Infoblox reported quarterly revenue of $87 million, up 34% year-over-year and about $6 million higher than analysts were expecting. Non-GAAP EPS came in at $0.12, up from $0.03 during the fourth quarter of 2014 and $0.02 better than the average analyst estimate. On a GAAP basis, Infoblox reported a loss of $0.08 per share.

Guidance from the company was a mixed affair. Revenue is expected to be between $86 million and $88 million during the first quarter, above an average analyst estimate of $82.2 million, while non-GAAP EPS between $0.05 and $0.06 is below the analyst consensus of $0.08.

While Infoblox's results and guidance were mostly positive, the company's conference call may be to blame for the decline in the stock price. Infoblox announced that its CFO was leaving the company after 11 years, but more importantly, questions about the sustainability of Infoblox's rapid growth were brought up by analysts. A product refresh cycle is currently driving a portion of the company's growth, and CEO Jesper Anderson, in an answer to the first of many questions related to the product refresh cycle, had this to say:

Look, refresh is a great tailwind to have for us and as we've said on earlier calls, we're very focused on making the most of it and upselling all of the opportunities we have around it. As you know we've said before, we don't break it out into details but we're very confident that we can grow our core market absent of refresh and we've seen that in the opportunities and individual deals that we've had.

Now what: With Infoblox still unprofitable on a GAAP basis, revenue growth is the main thing driving its stock price. Fourth-quarter revenue growth of 34% was far faster than annual revenue growth in the past couple of years: Revenue grew by 11.1% in fiscal 2014 and by 22.3% in fiscal 2015. Investors were apparently not convinced by the answers given by the CEO on the conference call, and they sent the stock tumbling as a result.