When last I wrote about networking up-and-comer F5 Networks (NASDAQ:FFIV), I decried the sell-off for what I thought was a stupid reaction to early stock options expensing. Had you followed my final musing of "if you've wanted to pick up some F5 . this might be your opportunity," you would have seen your shares skid about another six bucks . before pulling a U-turn and shooting up about 80% through mid-January.

OK, so maybe my timing wasn't perfect, but I had the right idea -- buying weak stocks of strong companies is one of those all-too-rare opportunities to exploit mispriced risk in the market.

Turning now to F5's first-quarter results, it looks like operations are still very much on track. Revenue climbed 47% from the year-ago level as firm product sales offset a little quarter-to-quarter weakness in security revenue. Profitability was quite good compared with the fourth quarter, though, and the gross and operating margins improved by 100 basis points and 60 basis points, respectively, as reported.

Although F5 has a strong presence in its segment of the networking market (well ahead of Nortel (NYSE:NT) and just behind Cisco (NASDAQ:CSCO)), Cisco seems to be making a renewed push at F5's core products. And then there's always the risk that other companies will get deeper into the mix through acquisitions.

Still, I'm not inclined to make too much of the Cisco threat just yet. After all, F5 got to where it's at through solid engineering and design, not by accident. So while I would never say that a company like Cisco isn't a clear and present danger, it is at least possible that Cisco's efforts will heighten overall customer interest in the segment, and perhaps it will be the marginal players that get hurt more than F5.

With about an 80% rise in its stock price in roughly six months, sentiment has definitely caught up to F5. In fact, you have to make some pretty aggressive assumptions to come up with a fair value target price that matches today's price -- though the fact that this company did more than double its free cash flow in the last fiscal year might help support those aggressive assumptions. All the same, I prefer investment scenarios more akin to where F5 was in late July or early August than today's situation.

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Fool contributor Stephen Simpson has no financial interest in any stocks mentioned (that means he's neither long nor short the shares).