In which situation do you need to select switches with a back-front (BF) airflow?

In a standard Top-of-Rack (ToR) data center deployment, switches are installed in the same rack as the servers they connect. For efficient cabling and management, the switch ports are aligned to face the same direction as the server network ports, which is typically the rear of the rack in the hot aisle. To maintain the data center's hot-aisle/cold-aisle cooling design, the switch must draw cool air from the cold aisle (at the back of the switch) and exhaust hot air into the hot aisle (from the port-side/front of the switch). This cooling scheme is known as back-to-front (BF) or port-side exhaust airflow.

A. This scenario, with ports facing the cold aisle, requires front-to-back (FB) or port-side intake airflow to pull cool air from the front and exhaust it to the back.
B. Aligning switch and server ports in opposite directions is an inefficient and non-standard cabling practice that complicates management and disrupts consistent airflow within the rack.
C. Similar to option A, if a switch's ports face the cold aisle, it requires front-to-back (FB) airflow, not the back-to-front (BF) airflow specified in the question.

1. HPE Aruba CX 8325 Switch Series Installation Guide (Edition 5

Document Part Number: 5200-6181a).

Page 11

Section: "Airflow": "The Aruba 8325 Switch Series is available with front-to-back (port-side intake) or back-to-front (port-side exhaust) airflow. ... For a Top-of-Rack (ToR) deployment where the switch and server ports are in the hot aisle

the back-to-front (port-side exhaust) models are used. The switch draws cool air from the cold aisle and exhausts hot air into the hot aisle." This directly supports the scenario described in the correct answer.

2. HPE Aruba CX 6400 Switch Series Installation Guide (Edition 4

Document Part Number: 5200-6179a).

Page 17

Section: "Airflow Direction": This guide reiterates the same principle for a different switch series: "For a Top-of-Rack (ToR) deployment where the switch and server ports are in the hot aisle

the back-to-front (port-side exhaust) models are used." This confirms the standard practice for ToR deployments requiring BF airflow.

3. HPE Aruba CX 10000 Switch Series Installation Guide (Edition 1

Document Part Number: R8P13-90001).

Page 16

Section: "Airflow": "The switch is available with front-to-back (port-side intake) or back-to-front (port-side exhaust) airflow. ... In a Top-of-Rack (ToR) deployment where the switch and server ports are in the hot aisle

the back-to-front (port-side exhaust) models are used." This provides further vendor documentation confirming the specific use case for BF airflow.