如何使用nginx和apache进行负载均衡？

I have three server. One is for load balance another two is for viewing my site. Normally when i load the load balancing ip it works fine. but when i click on some link to do another work it does not work. it gives me 404. In my other two server they have apache installed. What is the problem. How can i make my web page workable. my nginx load balancer default code is

upstream web_backend{
    server 192.168.33.2;
    server 192.168.33.3;
}

server{
    listen 80;

    location / {
        proxy_pass http://web_backend;
    }
}