apache reverse proxy tutorial Ubuntu 10.04

Rather than going into any further details and wasting your time to further search things on internet or giving lecture to read Eric Stevens non sense guide How to ask questions smart way which you might have faced while asking in forums.
Here is a small scenario where you would like to configure an Apache Reverse proxy.

You are having a server with a public IP and apache is running on it.Now you want to host your applications on LAN and also want them to be accessible on internet the important part is these applications are still running on the machines on LAN.

let say the websites are :

a)internal1.example.com should map to internal1.example.com
b)internal2.example.com should map to internal2.example.com
c)internal3.example.com should point to internal3 .example.com
d)internal4.example.com should point to internal4 .example.com

Following is network configuration

                           |--------------192.168.1.3 
                           |            (internal3.example.com)
                           |
                           |--------------192.168.1.4
                           |            (internal4.example.com)
  (Public IP )             |
            A--------------|
(reverse proxy server)     |
  (192.168.1.25)           |
example.com                |
                           |--------------192.168.1.1
                           |            (internal1.example.com)
                           |
                           |--------------192.168.1.2
                           |            (internal2.example.com)

I am using Ubuntu to host Apache the vhost definition in case of Debian based systems the definiton of websites is done on

/etc/apache2/sites-enabled/*.conf

where *conf corresponds to

internal1.conf internal2.conf internal3.conf internal4.conf

The vhost definition of each of these sites will be as follows

/etc/apache2/sites-enabled/internal1.example.conf

<virtualhost *:80>

      ServerAdmin webmaster@localhost
      ServerName internal1.example.com
      ProxyRequests off
      <proxy *>
      Order deny,allow
      Allow from all
      </proxy >
      ProxyPass / http://192.168.1.1/
      ProxyPassReverse / http://192.168.1.1/
</VirtualHost >

/etc/apache2/sites-enabled/internal2.example.conf

<virtualhost *:80>

      ServerAdmin webmaster@localhost
      ServerName internal2.example.com
      ProxyRequests off
      <proxy *>
      Order deny,allow
      Allow from all
      </proxy >
      ProxyPass / http://192.168.1.2/
      ProxyPassReverse / http://192.168.1.2/
</VirtualHost >

/etc/apache2/sites-enabled/internal3.example.conf

<virtualhost *:80>

      ServerAdmin webmaster@localhost
      ServerName internal3.example.com
      ProxyRequests off
      <proxy *>
      Order deny,allow
      Allow from all
      </proxy >
      ProxyPass / http://192.168.1.3/
      ProxyPassReverse / http://192.168.1.3/
</VirtualHost >

/etc/apache2/sites-enabled/internal4.example.conf

<virtualhost *:80>

      ServerAdmin webmaster@localhost
      ServerName internal4.example.com
      ProxyRequests off
      <proxy *>
      Order deny,allow
      Allow from all
      </proxy >
      ProxyPass / http://192.168.1.4/
      ProxyPassReverse / http://192.168.1.4/
</VirtualHost >

Note in all of the above vhost definitions I have dropped the options of Log files.
So if you apply to a production server add them in each of the vhost file.
Above is just to give you a clear cut example as how it can be working.
I run a very complex Apache setup so above is just a small example to help you.
Rest of the details can vary depending upon your configurations.