DNS settings frequently used two-step

 

A recording master station (corresponding to IPv4) @ host record (to resolve without www primary domain name) to IP

Master CNAME records (alias) www host record (to resolve the www primary domain) to example.com　　

 

Redirect station:

CNAME, www host record resolves to the main domain name

A, host records to resolve IP @

IP server corresponding to the master station to do 301 redirect.

 

Link: https://www.cnblogs.com/farwish/p/11584433.html