Method for mapping dynamically inside and outside network of server based on DDNS and NAT

The dynamic mapping method for internal and external server networks based on DDNS and NAT comprises: setting a special-developed internal-external gateway server or router, storing DDNS service program and the correlated NAT conversion service program; registering internal server DN and IP address message on the gateway server by NNDS client; to the DNS request for internal network server, using the NAT program to automatic allocate a public IP address; starting the NAT conversion to return the public IP address to complete the dynamic mapping.