Help with GPRS Gateway coding please

Hi All,

I currently have developed a product based on the CC9P9125, that includes a GPRS modem. I am using NetOS 7.5 and have a PPP interface set up so that I can get access to the internet via the GPRS modem.

I am now looking to expand on this functionality to allow the product to operate as a router such that other devices on the local LAN network, are able to also access the internet via the GPRS connection.

I am not quite sure of the best way to go about this.

I have started by calling NAIpSetIpForwarding(TRUE), and this works in so far as other units on the local LAN (with thier default Gateway set to the NetOS unit) are able to send packets on the LAN that get picked up and sent down the PPP interface. The problem is that these packets get sent on the PPP interface with the source IP of the local LAN.

I assume that I need to implement a NAT function within the NetOS router. At the moment I am thinking that I need to do something with IP packet filtering, and do some IP address translation there, but am not really sure where it is best to start.

Any advice to set me on the right path would be geatly appreciated.