The relationship between the geometrical structure of weight space and
replica symmetry breaking (RSB) in multilayer neural networks is stud
ied using a toy model. The distribution of sizes of the disconnected d
omains of solution space is computed analytically and compared to the
RSB calculation of the Gardner volume. We are able to show explicitly
that ergodicity breaking and RSB are not equivalent. Repeating these c
alculations using the cavity approach allows us to interpret the geome
trical meaning of a RSB ansatz.