upstream nginx1 {
    server 192.168.1.107:3001;
    server 192.168.1.107:3002;
    server 192.168.1.107:3003;
    server 192.168.1.107:3004;
    server 192.168.1.107:3005;
    server 192.168.1.107:3006;
}

server {
    listen       3001;

    location / {
        proxy_pass http://nginx1;
    }
}