I have several portals that use aliases to unify the associated domains into a single site.  I'm curious about the SEO implications of this and whether anyone has any input.  I've tried removing the aliases to see if it affected primary site's page rank or search ranks, with little or no impact being seen.  However, the alias practice does seem to violate the webmaster guidelines that google has posted.  I'm guessing I'm getting dinged for duplicate content due to the aliases, but I can't be sure.  Any wisdom would be greatly appreciated on this topic.

I'm still relatively new to DNN, so someone that understands IIS more than I, please explain to me how the db query works with and without the alias.  Does it provide a 301 or 302 redirect, if there is no alias associated, or is it more of a back office type of redirect that a search engine does not see.  If I could get an understanding of the mechanics, I may be able to figure out a work around.

One last thing about the aliases.  Is there a way to artificially put a 301 redirect into a dnn site.  I've not found any free modules that allow me to tell a crawler that I've moved the pages.  Is anyone aware of a way to do this without purchasing a commercial module?

Thanks for the help.