Eagle how to restore default autorouter settings?
Eagle autorouter parameters can be stored in .ctl files.  There is probably at least one example that comes with Eagle, and you can save the current settings to a .ctl file and them restore them later any time you want.

The Eagle defaults are pretty useless.  You really need to tweak the autorouter for the kind of job you are doing.  For example, two layer with as much ground as possible on the bottom layer and four layer will need different strategies.