DDNS application

As shown in Figure 49, DDNS works on the client-server model.

• DDNS client—A device that needs to update the mapping between its domain name and IP address dynamically on the DNS server when its IP address changes. An Internet user typically accesses an application layer server such as an HTTP server or an FTP server by using the server's domain name. When its IP address changes, the application layer server runs as a DDNS client. It sends a request to the DDNS server for updating the mapping between its domain name and its IP address.

• DDNS server—Informs the DNS server of latest mappings. When receiving the mapping update request from a DDNS client, the DDNS server tells the DNS server to re-map the domain name and the IP address of the DDNS client. Therefore, the Internet users can use the same domain name to access the DDNS client even if the IP address of the DDNS client has changed.

With the DDNS client configured, a device can dynamically update the latest mapping between its domain name and IP address on the DNS server through DDNS servers.

	NOTE: The DDNS update process does not have a unified standard but varies by DDNS server that the DDNS client contacts.