In double sided PCBs it is difficult to solder through hole components like IC bases, headers, etc. in the top layer. Normally the Eagle autorouter places the solder pads on both sides. That is, in a through-hole IC base some pins should be soldered in the bottom layer and some in the top layer. But I need routes in the top layer and vias.
Is there a way in the Eagle autorouter to tell it to avoid soldering in top layer? Please see the "Design requirements for hobby boards" and "Turned-pin IC sockets" sections of Joe's Hobby Electronics: Making double-sided PCBs for more information about the problem.