  We consider the following two problems: classical domain walls in the $N=1^*$
mass deformation of the maximally supersymmetric Yang Mills theory, and
D-strings as external magnetic sources in the context of the AdS/CFT
correspondence. We show that they are both described by Nahm's equations with
unconventional boundary conditions, and analyze the relevant moduli space of
solutions. We argue that general `fuzzy sphere' configurations of D-strings in
AdS$_5$ correspond to Wilson-'t Hooft lines in higher representations of the
dual SU(n) gauge theory.
