BIND Version 8 Features

Wondering about the latest version of BIND? Wonder no more. Mr. Harari is back this month to tell us all about it.
Dynamic Updates

BIND 8 allows authorized hosts to send the zone master server an UPDATE message. An UPDATE message can add, delete or change record information in the zone's database. The machine that sends the update message tries to find the master server for the zone from the zone's NS records. If the message is received by a slave server instead of the master server, the slave server should forward the message to the master server.

Dynamic updates are a good thing for hosts which get their IP addresses dynamically from a RARP (reverse ARP) or DHCP (dynamic host configuration protocol) server. These hosts can send an update message to the DNS server after they get their IP address from the DHCP/RARP server. The new resolver library routine, ns_update, is used by programs to send DNS update messages to the server. BIND 8 is shipped with a command-line utility, nsupdate, that gives the ability to send update messages to the zone's master server. By default, no one is allowed to dynamically update a zone; the configuration file keyword allow-update gives the system administrator the ability to configure the hosts which can send update messages for each zone. This update can help DNS and WINS to live together on the same network, since WINS also uses a dynamic-update method.

zone  "my.domain.sela.co.il" {
                    type master;
                    file "db.my.domain";
                    allow-update { 10.1.1.1;  };
                   };

This example lets the host 10.1.1.1 send update messages containing information on the my.domain.sela.co.il zone.

Conclusion

BIND 8 has many nice features, some of them needed by many network administrators. Since major security holes were discovered in earlier versions of BIND, upgrading to BIND 8 is almost a must. There are still stable older versions, such as 4.9 and later, but these do not support all the functions mentioned here.

Eddie Harari (eddie@sela.co.il) works for Sela Systems & Education in Israel as a senior manager and is involved in some security projects. He has been hacking computers for 13 years.

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