Checkpoint securemote VPN with redhat

[gekko2004]

I need to configure a VPN to access a remote server in order to run an client-server app. I am the client, the server requires me to use checkpoint securemote. I installed the only existing securemote linux version on the only reliable redhat 7.2-18 kernel, and could establish the VPN connection. But the application which sends request through the VPN uses high ports, and it seems that I have a pb when unencapsulating some packets. I send my request on port 9074 and the server gets it. The server sends me back the response on port 1112, but I can't receive it. When I log the received packets all I can read is that they are sent on ports are 2746 and 500 (those used by securemote). But my app client (who listens to port 1112 as expected) never catches any answer.
It works on a Windows box in the same network, so I don't think my firewall is involved
Do I need any specific configuration to have ports forwarded correctly to the destination within the VPN, or do you have any other idea on the pb ?
Thank you for your help

[lakerdonald]

It works on a Windows box in the same network, so I don't think my firewall is involved

From that it sounds to me like you have a hardware firewall, correct? This is a stupid suggestion, but did you check to see if a software firewall (i.e. iptables) is perhaps the culprit?
It's just a thought,
lakerdonald