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What exactly do these terms mean? I intuitively understand them to mean airflow direction can be reversed or changed.

The Cisco 3900 Series routers ship with a default fan assembly that drives “business-to-bezel” airflow in the router chassis. An alternate, optional fan assembly provides a “bezel-to-business” airflow and includes an air filter appropriate for dusty operation environments or Network Equipment Building Standards (NEBS) installations.

Source: http://www.cisco.com/c/en/us/products/collateral/routers/1900-series-integrated-services-routers-isr/ordering_guide_c07_557736.html

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The bezel is the decorated plastic panel making your router or switch look nice in the data center. Here's an drawing from Cisco:

Cisco 2600 Bezel

So the bezel side of a device is often called the front. The back, containing all the interfaces is in this case called the "business side", because it is the important side. You bought the device to connect stuff to, not for its decorative appeal...

Fans blowing "business to bezel" will take air in at the business/back side and blow it out the front/bezel side. A correct airflow direction is important for cooling, and depends on how your datacenter is cooled and how the device is put in the rack.

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  • What's confusing is that some equipment has the business side on front and back like 7200 VXRs Jun 30 '15 at 11:11
  • What's more confusing is on some equipment the "business" side is the bezel side, like almost every switch ever. I prefer the terms "port side intake" or "port side exhaust" when talking about switch airflow. Jun 30 '15 at 13:01
  • I had also heard years ago that the decorative side is the back and not the front where all interfaces should be located. The only thing we can be sure about is which side faces up. :-) Jun 30 '15 at 20:59
  • The 7200VXR "business" side is the PA slots. And even "up" can be in question: I've hung 2800's on walls. Which side is "up" then? (bezel up, top cover out)
    – Ricky
    Jul 1 '15 at 2:51

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