Can I use my Mac as a proxy for Ubuntu? I have an Ubuntu PC (IP: 132.195.2.2) set up which should be connecting through a switch to my iMac (IP: 132.195.2.1) in order to gain internet access. The iMac has "share internet connection" turned on. I've added the iMac's IP in the gateway, DNS and search domain field in the configuration for the eth0 on the Ubuntu PC. I also added the iMac's IP as proxy for all services. They can ping each other PC/Mac, but the only thing my Ubuntu PC gets when calling any URL is my addressbook server web admin page.

Any idea what I've done wrong or how to set this up the right way?
The mac firewall must be disabled for this to work. 

You can follow this guide if needed for NAT setup on the mac and verification of ubuntu settings.