by Sal Hernandez » Mon May 14, 2012 9:30 am
You do have some control over the auto router. Go to View > User Preferences > Routing and Spacing Rules. Change the settings in the Autorouter layer bias to avoid using specific layers. You can't avoid routing on the outer layers with surface mount parts but with a mainly through hole board it works pretty well. You may still get a few traces on layers with Do not use selected as the layer bias, but not nearly the number you would get without the setting. Any time you make changes in the User Preferences make sure to select Apply then OK to save the changes. It does matter.
Regards,
Sal Hernandez
Software Support Engineer I
Sunstone Circuits
13626 S. Freeman Road
Mulino, OR 97042
Phone: 503-829-9108 x226
Fax: 503-829-5482