Use a rack grounding kit and a ground conductor that is carried back to earth or to another suitable building ground.
All Extreme Networks switches are designed with mounting brackets that provide solid metal-to-metal connection to the rack. If you do not use equipment racks, you can attach wiring terminals directly to the mounting brackets for appropriate grounding. At a minimum, follow these guidelines:
Ground equipment racks to the earth.
CAD weld appropriate wire terminals to building I-beams or earth ground rods.
Use #4 copper wire.
Drill and tap wire terminals to equipment racks.
Position the earth ground as close to the equipment rack as possible to maintain the shortest wiring distance possible.
Properly test the quality of the earth ground.