How to setup FB's Katran load balancer

I'm trying to setup Katran Load balancer from https://github.com/tehnerd/katran on Ubuntu, but I am confused with the example explained and how the packets are forwarding through IPIP interface between LB and real servers. The example doc has some confusing tcp dumps and ips. I couldn't find out how many NICs or IPs I need.

I couldn't find any other documentation elsewhere.