Nahm's equations, $N=1^*$ domain walls, and D-strings in $AdS_5 x S_5$

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 correspond to heavy monopoles in higher representations of a non Abelian gauge group.