IP forwarding or sharing via /etc/NETWORK?

Hi to you all, and here's my situation: My main machine is connected to the internet via dhcp. I installed a second network interface card into this PC (A) and connected it via a RJ45 patch cable to a second PC (B). My goal is to get B an internet connection using A. So this is my main question: If this is possible, can I do it with adjusting /etc/NETWORK and booting settings (in my case /etc/rc.local)? (I'm using dyne:bolic 2.5.2, an older distro based on a 2.6.18 kernel. Why? I like it and I'm able to work fine with just a system cd and an usb flash drive.) Due this is my first post, I did some quick searching but didn't found a comparable thread. If there is one, just post the link and please... do not hold this thread against me. ;) Thank you in advance, Gifti

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