At last I got it ! Well, to be honest I will say Maxim Dounim helped me thru my logs. In the end it was so simple ::: My load balancer in front of my Nginx's always looked thru IP so no host name ever matched any of my server_name's. Solution simple :: Do the balancer refer to nodes thru a locally resolved hostname also put as a new server_name. ...........simple like crazyness when it comes.

The thing now is I have following block and it works quite right. But If I mean to use the commented return 444 instead of the rewrite ==> al my web start returning 503 !!! and nothing's functioning .......always the strange things to me.

server {
listen 80 default_server;
server_name _;
error_log /var/log/nginx/000default-error.log error;
location / {
proxy_set_header Host $host;
rewrite .* http://somewherelse.net permanent;
#return 444;
}
}