Until now we've treated DNS requests as forward facing lookups, translating resource names like www.example.com to an IP address. However, services can also ask a DNS server to resolve information in the opposite direction by providing an IP address and want to know what name it's associated with. Reverse lookups such as these are especially useful for logging or authentication and security purposes. For example, a system can query a DNS server to verify that a client really is connecting from the system they claim. To accommodate such requests, this recipe shows you how to write a reverse lookup zone file.
This recipe requires a CentOS system with BIND installed and configured as described in the previous recipes. Administrative privileges are also required, either by logging in with the root account or through the use of sudo.