Bind forwarder option

What is DNS forwarder?

DNS forwarder is like an upper DNS servers. If some DNS server receives a query which is not owned as authority, the DNS server can forward the request to other DNS servers. Those other DNS servers who work as a resolver instead of original DNS server is called forwarder.

How to configure a forwarder on bind?

Edit /etc/bind/named.conf.options like below.

options { 
        directory "/var/cache/bind"; 

        // If there is a firewall between you and nameservers you want 
        // to talk to, you may need to fix the firewall to allow multiple 
        // ports to talk.  See http://www.kb.cert.org/vuls/id/800113 

        // If your ISP provided one or more IP addresses for stable 
        // nameservers, you probably want to use them as forwarders. 
        // Uncomment the following block, and insert the addresses replacing 
        // the all-0's placeholder. 

        forwarders { 
                8.8.8.8; 
        }; 

        auth-nxdomain no;    # conform to RFC1035 
        listen-on-v6 { any; }; 
};

What is the difference, forwarder and parent domain?

A DNS server acts to query some domains to root dns servers at first, maybe called deligation. But, I can't explain the difference about forwarder and deligation. I will check about this difference in the future.