Allow recursion only for internal clients on public DNS

<yambe:breadcrumb>Bind_DNS_server_configuration|Bind DNS</yambe:breadcrumb>

Allow recursion only for internal clients on public DNS

To allow recursion only for internal clients on public DNS use:

   acl internal { 127.0.0.1; 172.16.0.0/12; 192.168.0.0/16; 10.0.0.0/8;};

   options {
   ...
   recursion yes;
   allow-recursion { internal; };
   ...
   };