source NAT (SNAT)

Source Network Address Translation(SNAT) is a NAT method for connecting private networks with multiple IP addresses to the Internet when only one IP address is available for this purpose.

With this connection, the IP addresses of the various clients are stored in the NAT table of the Internet router via which the local network is connected to the Internet. For each LAN port with the associated LAN address, the NAT table contains the WAN port.

If a LAN client wants to connect to the Internet, it sends a data packet with the IP address and the port number to the Internet router, which exchanges the IP address of the local network for the public Internet address and the WAN port number. The router forwards the data packet with the new IP address and port number to the Internet and stores the changes in the NAT table. The changed data packet reaches the server on the receiving side, which then sends a response to the client. The response packet passes through the Internet router, which performs another address exchange and forwards the data packet with the original LAN address to the client in the local network.