The ornamental design for a router, as shown and described.
FIG. 1 is a front perspective view of a router showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a left side view thereof; and,
FIG. 6 is a top view thereof.
The uneven-length broken lines immediately adjacent to the shaded area represent the bounds of the claimed design and form no part thereof. The even-length broken lines depicting the buttons, outlet openings, vents, and remainder of the router form no part of the claimed design.