|dns is required for tcp/ip name resolution. for example you can have physical internet conneciton but if no dns setting you can't browse the internet.|
you put in the domain name for the web page in public dns so others on the internet can find the web page.
Though your ISP provides dynamic ip its public. Your server should be on private ip. Public interface is referred to as wan. Local interface is referred to as lan.
if running AD you configure the server to provide local ip to your workstations
it is normal to configure the first AD server with dns server and dhcp server. though you can run a single server it is highly recommended you have two AD servers for AD failover.
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