  We study the origin of a CME-related shock within the LASCO C3 field-of-view
(FOV). A shock originates, when a CME body velocity on its axis surpasses the
total velocity $V_A + V_{SW}$, where $V_A$ is the Alfv\'en velocity, $V_{SW}$
is the slow solar wind velocity. The formed shock appears collisionless,
because its front width is manifold less, than the free path of coronal plasma
charged particles. The Alfv\'en velocity dependence on the distance was found
by using characteristic values of the magnetic induction radial component and
of the proton concentration in the Earth orbit, and by using the known
regularities of the variations in these solar wind characteristics with
distance. A peculiarity of the analyzed CME is its formation at a relatively
large height, and the CME body slow acceleration with distance. We arrived at a
conclusion that the formed shock is a bow one relative to the CME body moving
at a super Alfv\'en velocity. At the same time, the shock formation involves a
steeping of the front edge of the coronal plasma disturbed region ahead of the
CME body, which is characteristic of a piston shock.
