A while ago I wanted to combine the blog posts I've written about the default routes in OSPF into a single wiki article. As I started to investigate the various options you have to generate default routing in OSPF (including stub areas and not-so-stubby areas), the text quickly became too long and resulted in July IP Corner article "The OSPF default mysteries".
Ivan Pepelnjak, CCIE#1354, is the chief technology advisor for NIL Data Communications. He has been designing and implementing large-scale data communications networks as well as teaching and writing books about advanced technologies since 1990. See his full profile, contact him or follow @ioshints on Twitter.