“You have to be very careful when using Sub Domains because if the content on your sub Domain is too close to the main site, and since search engines look at sub Domains as separate sites, it will degrade your rank because it will consider this as multiple sites with the same content.”
If my site has lots of sub domain, then Google can be banned my site and effect on my site ranking?


 

Mirror sites almost copied sites and subdomain sites mean you make site in a website for example "example.com" is a site and you make site on it "yourwebsite.example.com" you can share anything on it.