I have created multiple Sites at root level and setup for all sub domain to respective sites.

Issue is that any of the subdomain page is working in main domain

Example:

Main Domain : XYZ.com
Sub Domain : ABC.XYZ.com/SubDomainPage

Sub domain page XYZ.com/SubDomainPage is working.

I want to restrict this link(XYZ.com/SubDomainPage) to page not found how can i do ?

I have setup the subdomain & maindomain in Culture and Hostnames.
Both domain & subdomain are setup in individual sites.