Using Nginx as a load balancer

I am new to load balancing and i do have some questions:P

Beware : Noob alert but every once start from somewhere

Lets take this for example

upstream web_rack {
        server 10.0.0.1:80;
        server 10.0.0.2:80;
        server 10.0.0.3:80;
    }

While its obvious that i need to host a replica of my website on 10.0.0.1 , 10.0.0.2 and 10.0.0.3 , do i need to setup domain(BIND ) on each of them or only on the main server.

If i understand well , there is one main server + 3 backend server that do load balancing

Shred some light on this guys

Thanks in advance