How to check the headers of a Site using a custom IP address
This will check the site blog.ricardoamaro.com against the IP 50.19.98.136 on Port 80 :
~$ curl -Is -H "host: blog.ricardoamaro.com" 50.19.98.136:80
HTTP/1.1 200 OK
Server: nginx
Content-Type: text/html; charset=utf-8
X-Drupal-Cache: HIT
Etag: "1372246782-0"
Content-Language: en
X-Generator: Drupal 7 (http://drupal.org)
Cache-Control: public, max-age=0
Last-Modified: Wed, 26 Jun 2013 11:39:42 +0000
Expires: Sun, 19 Nov 1978 05:00:00 GMT
Vary: Cookie,Accept-Encoding
X-AH-Environment: prod