This example illustrates a relatively complex dns configuration. The fictitious company has a connection to the Internet via UUNet which allows them to host their own sendmail, www and dns servers. They have a firewall which protects their internal networks. The system is configured with a backbone connecting three departments which have their own network. A server on the backbone provides dns to all the computers on the internal networks.
The following zone files are representative of what might be found to configure the dns servers.