The Dynamic DNS is used to access the gateway remotely when the DSL or Cable Internet service has a dynamic IP address setting.
The gateway is located using the services of DynDNS (http://www.dyndns.com/).
The Dynamic DNS setting requires an account with DynDNS. When the box is checked to enable the DynDNS the DynDNS hostname, username and password must be entered.
Subsequently, the DSL or cable router can be located using the hostname URL which is resolved to an IP using the DynDNS server.