In the EX4300 switches the fan modules are hot-insertable and hot-removable field-replaceable units (FRUs).

All the EX4300 switches, except EX4300-24T-S, EX4300-24P-S, EX4300-32F-S, EX4300-48T-S, and EX4300-48P-S switches are shipped with two fan modules pre-installed in the rear panel of the switch. EX4300-24T-S, EX4300-24P-S, EX4300-32F-S, EX4300-48T-S, and EX4300-48P-S switches are not shipped with pre-installed fan modules; you must order them separately. Each switch can accommodate two fan modules in the fan module slots on the rear panel of the switch. The fan module slots are numbered 0 and 1 and each slot has a fan icon next to it.