Power supply
There are three modes of operation supported by Cisco Catalyst 9400 power supplies. In all the modes the power supplies can be of different wattage and type whether AC or DC.
Redundant N + N mode
The Cisco Catalyst 9400 Chassis also supports N + N redundancy with N independent input circuits and safeguards against failure of N (+N) of the circuits as opposed to power supply unit failure.
Redundant N + 1 mode
The Cisco Catalyst 9400 Chassis also supports N + 1 redundancy with N independent input circuits and safeguards against failure of one (+1) of the circuits as opposed to power supply unit failure.
Combined mode
In this mode the power available for the entire chassis is equal to the sum of the output power of both of the power supplies multiplied by the share ratio.
P = Power output of one power-supply unit
Total combined mode power = P + (N-1) * P * (share ratio)