Resistive switching in aluminum-polymer diodes has been investigated by noise measurements. Quantitative criteria to characterize the diode states are: (i) Pristine state shows I ¿ Vm with m ˜ 6 at higher bias typical for tunneling. The resistance is very high, 1/f noise is very low, but the relative 1/f noise, fSI/I2 = C1/f is very high. (ii) Forming state is a time-dependent soft breakdown in the Al-oxide that results in random telegraph signal noise (RTS) with a Lorentzian spectrum or in multi-level resistive switching (MLS) with a 1/f3/2 or 1/f-like spectrum. (iii) The H- or L-state shows I ¿ Vm with m = 1 for V <1V and 3/2 <m <2 for V > 1V. Deviations from ohmic behavior are explained by space charge limited current in the polymer. Reliable H- and L-states show pure 1/f noise, a resistance R that changes by at least a factor 30 and 1/f noise that follows the proportionality: C1/f ¿ R with a proportionality factor aµ(cm2/Vs) of the same level as observed in metals, polymers and other semiconductors. C1/f ¿ R is explained by switching of the number of homogeneous conducting paths in parallel. Deviations in C 1/f ¿ R are also explained. In the pristine state and even in the H-state, only a fraction of the device are is carrying current and switching seems to be at spots of the Al/Al2O3/polymer interface.