5.5.2 NAT
Network address translation (NAT) can be used when some hosts on a private network
have been assigned with local IP addresses (that is, private IP addresses used
only on the private network), but expect to communicate with hosts on the Internet
(without encryption).
Common scenario: A user expects to access a camera on the LAN of the device
through the public network to view the current driving conditions of the vehicle.
The camera address is 192.168.2.100, and the open port 18000 provides video
services.
1. Click "Firewall >> NAT", and select "DNAT" for "Action", and "Outside" for
"Source Network". Select "IP PORT to IP PORT" or "INTERFACE PORT to IP PORT" for
"Translation Type". The public IP address obtained through dial-up is not fixed,
so "INTERFACE PORT to IP PORT" is more convenient. Select "TCP" for "Transmit
Protocol" because video services are transmitted over TCP. Select "cellular 1"
(dialup interface for the cellular network) for "Interface" and set "Port" to
"20000". Set "IP Address" and "Port" under "Translated Address" to "192.168.200"
and "18000" respectively. Click Apply & Save.
The gateway redirects the TCP service destined for port 20000 of the cellular 1
interface to the internal IP address 192.168.2.100 and port 18000, to enable
access to the internal services.
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