The Dow Jones Industrial Average (DJINDICES:^DJI) was up by a modest 0.1% in afternoon trading. Twenty of its 30 tickers were trading in the green, and only one stock had fallen more than 0.8%.

That outlier was Cisco Systems (NASDAQ:CSCO). Shares of the networking giant were down 0.85%, making it the Dow's biggest loser as of 2 p.m. EDT.

So what's wrong with Cisco this time? The short answer is, absolutely nothing.

This is yet another random walk down Wall Street. Cisco's weakness today is not an investable event, nor is it any reason to change whatever investment thesis you had on the stock yesterday.

The lack of market-moving Cisco news this morning is truly astounding. Breathtaking, even.

  • The company hasn't issued a press release since Tuesday.

  • The CSCO ticker hasn't come up as a point of discussion in any major media outlet since yesterday.

  • This terrifying share price drop rides on extremely weak volume. Cisco shares are on pace for less than half their average trading volume today. Not even the bears are passionate about this.

  • How about a slightly longer-term view of Cisco's Dow-leading fall? The stock is down to prices not seen since ... last Friday. Yikes, right?

There's really nothing wrong with Cisco today. Just kick back and relax in the soothing presence of this Cisco networking rack. Source: Cisco Systems.

If there's any reason at all for Cisco's decline this time, it would be that network security rival Palo Alto Networks (NYSE:PANW) reported a nice quarter last night. Palo Alto grew sales much faster than Cisco's security division did in the comparable period, so the smaller company is taking some market share from Cisco here.

But even so, Palo Alto's report shouldn't scare Cisco investors. The security specialist reported $151 million in third-quarter sales. Cisco's overall third-quarter sales stopped at $11.5 billion. It's like a gnat threatening to strangle an elephant.

Breaking out Cisco's security revenue isn't easy to do, since the company doesn't report separate numbers for this subdivision. But the core of Cisco's current security operations comes from last fall's acquisition of Sourcefire, which reported just $65 million in quarterly sales before Cisco absorbed it. In short, Cisco isn't risking much of its business, even if Palo Alto rises up to dominate the security market. Which it probably won't anytime soon.

So Cisco didn't do anything wrong today. The company isn't facing any significant threats that weren't there last night. There's no reason to panic. And yet, the stock manages to become the Dow's biggest loser on an otherwise hunky-dory market day.

Go figure. Just another reason to take the long view and ignore the market's daily squiggles.

Anders Bylund has no position in any stocks mentioned. The Motley Fool recommends Cisco Systems and Palo Alto Networks. Try any of our Foolish newsletter services free for 30 days.

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