Add the following lines to /etc/named.conf, (edit ip's, domain, dir)
options {
directory "/var/named";
check-names response warn;
notify yes;
};
zone "your.domain.here" {
type master;
file "db.subdomain";
};
# For secondary name server setup, add this line also...
zone "your.domain.here" {
type slave;
masters { ip.address.of.master(s); };
};