Put a single robot.txt file in the root of the entire DNN instance to cover all portals.

But note that a robots file is not the same thing as a sitemap, and Marc, you seem to be talking about both in the thread here.

DNN auto-generates a sitemap file as domain.com/sitemap.aspx. It's not a good one however as it gives all pages the same priority. There are third party modules that also do sitemaps... check on snowcovered.com or the dnn marketplace here. 

Rob

Robax,

I am using the Googlesitemap provider of iFinity and if I understand you correctly this means that I should have 1 robots.txt in the root of my DNN installation which has to lines, like this:

Sitemap: http://www.domain1.com/googlesitemap.axd
Sitemap: http://www.domain2.com/googlesitemap.axd

Thanks in advance.