  A significant number of the known multiple exoplanetary systems are
containing a pair of giant planets engaged in a low order mean motion
resonance. Such a resonant condition protects the dynamics of these planets
resulting in very stable orbits. According to recent studies the capture into a
resonance is the result of a planetary migration process induced by the
interaction of the planets with a protoplanetary disk. If the migration is slow
enough (adiabatic) next to a mean motion resonance, the two planets will also
be in apsidal corotation.
  The recently refined orbital parameters of the system HD 128311 suggest that
the two giant planets are in a 2:1 mean motion resonance, however without
exhibiting apsidal corotation. Thus the evolution of this system can not be
described by an adiabatic migration process alone.
  We present possible evolution scenarios of this system combining migration
processes and sudden perturbations. We model migration scenarios through
numerical integration of the gravitational N-body problem with additional
non-conservative forces. Planet-planet scattering has been investigated by
N-body simulations.
  We show that the present dynamical state of the system HD128311 may be
explained by such evolutionary processes.
