htaccess request forwarding if internal ip

Is there a possible htaccess directive that can transparently forward request from index.php to index_internal.php if the request is coming from an internal ip range?

From stackoverflow

• Something like this should do it (obviously change the IP address to match your network):

  RewriteCond %{REMOTE_ADDR} ^192\.168\.
  RewriteRule index.php index_internal.php
  

  If you want an actual header then make it RewriteRule index.php index_internal.php [L,R,QSA]

• RewriteEngine on
  
  RewriteCond %{REMOTE_ADDR} ^192\.168\.1\. [OR]
  RewriteCond %{REMOTE_ADDR} ^10\.15\.
  RewriteRule ^index\.php$ index_internal.php [R,NC,QSA,L]
  

  What this does:

  start mod_rewrite engine (you may have that already)

  if (client IP address starts with "192.168.1." [or]

  client IP address starts with "10.15.")

  and page name is index.php ([n]ot [c]ase sensitive), [r]edirect to index_internal.php, [q]uery [s]tring [a]ppend (i.e. index.php?foo=bar becomes index_internal.php?foo=bar), [l]eave processing.

  Modify as needed for IP address blocks.

• ok here's my code (no redirect) based on wikipedia's private network list

  RewriteEngine on
  RewriteCond %{REMOTE_ADDR} ^10\. [OR]
  RewriteCond %{REMOTE_ADDR} ^172\.[1-3]{1}\d{1}\. [OR]
  RewriteCond %{REMOTE_ADDR} ^192\.168\.
  RewriteRule ^index\.php index_internal.php [NC,QSA,L]
  

  Piskvor : Nice idea! Beware though: not all that's in private range must be necessarily inside your network - for example, I've seen configs where 10.1.255.255 was internal network and 10.4.255.255 was another, less trusted network via VPN. I'd allow only as much access as is necessary.

  ken : i only need to detect if my web application is accessed via public or internally just to set some constants especially redirection host for our single sign on app