Non-Internet "named.ca" file root hint.

[Truong Tan Son]

Dear Sir,

I am using Bind for local Dns (Non-Internet connection), but
    don't know how to make "named.ca" file for Root server (master), and Subdomain servers (slaves).

Supposes my domain is named "domain", designate to the machine "root", IP address: 1.2.3.4.
 
--named.ca--
@    IN    SOA    root.domain.    man.domain.    (    
        $serial    $refresh    $retry    $expire    $TTL
)
domain.                    IN        NS    root.domain.
root.domain.             IN        A       1.2.3.4

sub.domain.              IN        NS    slave.sub.domain.
slave.sub.domain.      IN         A      5.6.7.8

*Root server (root.domain, IP: 1.2.3.4)
   -- named.conf --
    zone "domain" in {
            type master;
            file "named.ca";
          };

*Slave server (subdomain):
   -- named.conf --
   zone "domain . " in {
            type master;
            file "named.ca";
          };
    zone "sub.domain" in {
            type slave;
            file "db.sub.domain";
            masters {1.2.3.4; };
        }


Please give me advice.


Thanks you and best regards,
--