It's better now : my webhosting allows to create subdomains outside the DNS zone, and i didn't see it ; so now, after creating the sudomain mychild.myportal.com, i can view images like mychild.myportal.com/myimage.png. But Not Home page... !!! :
My dnn sub-site contains this aliases configuration in advanced settings :
1. mychild.myportal.com (Primary checked)
2. myportal.com/mychild (Primary not checked, CanonicalUrl option checked)
When i test both URLs : First is KO with "Unavailable server error" page, second is correct with home page displayed.
I tried to configure web.config to customize error details (CustomErrors=off...) rather than classic "Unavailable server error" page, but i can't see error content from subdomain url, it seems working only for a domain url...
So today, i can see images from subdomain, but not viewing aspx pages... Any idea please ?