nginx not caching request from IIS 6

nginx reverse proxy to IIS6 running asp and sql server not caching requests

nginx.conf is as follow

--------------------------------------------------------------------------------------------------------------------------------------------
For more information on configuration, see:
# * Official English Documentation: http://nginx.org/en/docs/
# * Official Russian Documentation: http://nginx.org/ru/docs/

#user nginx;
worker_processes 1;

error_log /var/log/nginx/error.log;
#error_log /var/log/nginx/error.log notice;
#error_log /var/log/nginx/error.log info;

pid /run/nginx.pid;


events {
worker_connections 1024;
}


http {
include /etc/nginx/mime.types;
default_type application/octet-stream;

proxy_cache_path /nginx/cache levels=1:2 keys_zone=mycache:1024m
max_size=1500m inactive=600m;
proxy_cache_key "$scheme://$host$request_uri";
proxy_ignore_headers "Set-Cookie";



log_format main '$remote_addr - $remote_user [$time_local] "$request" '
'$status $body_bytes_sent "$http_referer" '
'"$http_user_agent" "$http_x_forwarded_for"';

access_log /var/log/nginx/access.log main;

--------------------------------------------------------------------------------------------------------------------------------------------

def.conf under conf.d is as follows

server {
listen 80;
server_name localhost.localdomain;

location / {
proxy_pass http://192.168.11.150:80;
proxy_cache_valid 200 302 10m;
proxy_cache_valid 404 1m;
proxy_cache_bypass $arg_nocache;
proxy_cache_bypass $http_pragma $http_authorization;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_redirect off;
client_max_body_size 10m;
client_body_buffer_size 128k;
proxy_connect_timeout 90;
proxy_send_timeout 90;
proxy_read_timeout 90;
proxy_buffers 32 4k;
proxy_busy_buffers_size 64k;
proxy_temp_file_write_size 512m;
}

--------------------------------------------------------------------------------------------------------------------------------------------

any clues? im new to nginx and playing around with it to be familiar with it at least

running on fedora 20