[Editor: This story was updated to add more details about sales of Cisco white-box Nexus switches to Facebook.]

Cisco Systems Inc. (Nasdaq: CSCO) is quietly building its own "white box" strategy to combat a developing market for open Software Defined Networking (SDN) products and has sold large orders of Cisco switches configured as white boxes to Facebook (NYSE: FB), according to industry sources.

So what's up with this? It's clear that Cisco wants a backup strategy to combat the advent of SDN and white boxes, in which generic hardware switching platforms are provided as "bare metal" so that customers can load their own software and customize the product. Cisco has responded to the SDN threat with its Application Centric Infrastructure (ACI) initiative, which makes its hardware more programmable by selling you an SDN product -- the Applications Policy Infrastructure Controller (APIC). But there's also a backup plan: Cisco is developing a secret, behind-the-scenes white-box strategy, according to several sources.

White boxes are built with off-the-shelf switching chips known as merchant silicon, and loaded with open SDN software to run many networking applications. But how to differentiate? The new marketing buzz phrase that has taken over the industry is "brite box," in which you take a white box and apply your own branding, special services, and support twist to please the customer. The differentiation becomes a "branded white box," or "brite box."

Industry sources tell me that this is Cisco's backup strategy: Use the Nexus 3000 switch, known as the 3K, as a brite box.

And there's more: Several industry sources say it's "common knowledge" that Cisco shared technical details and collaborated with Facebook to sell it a bunch of Nexus switches that could be loaded with Facebook's own Facebook Open Switching System (FBOSS) operating system. One source says these orders could have amounted to millions of dollars worth of Nexus switches loaded in white-box fashion.

A Cisco supplier with connections inside the company elaborates on the strategy. Here's my summary of what they told me:

You take the Nexus 3K, which is built on Broadcom merchant silicon. That is, it's close to a brite box because it uses commodity chips. If it turns out that the market really does move toward white boxes -- or brite boxes -- that means the 3K might be a better fit than, say, a fully loaded 9K Nexus rack running ACI, which will run you up to a quarter of a million dollars.

If the white-box and brite-box markets become more of a threat than previously estimated (Cisco has been dismissive of these threats), Cisco could change the pricing model on the 3K hardware, switch the 3K over to a white-box model, and provide high-touch support using a "one throat to choke" mantra as your hand-holding brite-box technology integrator.

It may already be happening. The 3K price has been dropping and is regularly available at 50% off list-price from the channel. Cisco is becoming more aggressive in selling support packages, says one of my sources.

Although Cisco doesn't disclose any official brite-box programs, if you read between the lines it's clear it has one. As much as Cisco seems to dislike white boxes, the company spends a lot of time talking about them. Cisco Chairman and CEO John Chambers has gone on long harangues about white boxes on corporate conference calls, and Cisco executives made a video to defend their product against the onlaught of white-box and brite-box mania.

In this slick propaganda video, Rob Lloyd, Cisco's President of Development and Sales, and Frank D'Agostino, Senior Director of Technical Marketing, explain how the cost savings in white boxes are a myth. But they also point out that Cisco is thinking about how to compete with the white boxes by providing better integration and support.

In other words, Cisco has a brite-box strategy.

If this sounds a lot like the brite-box strategies being discussed by HP and Dell, it is. But there is more at stake for Cisco, because Cisco is the market leader, and HP and Dell are just trying grab back market share in the datacenter switching market. Put it all together, and it makes for a fun dogfight coming in the white-box-brite-box market.