You can do this by modifying httpd.conf manually. See the "Serving the same content on different IP addresses" section in the Apache docs for more information:
http://httpd.apache.org/docs/2.0/vhosts/examples.html
Basically, just add the second address to the appropriate virtualhost(s). Assuming you're familiar with SSH, all you'd do is
Code:
nano /usr/local/apache/conf/httpd.conf
and then add the IP address to the virtualhost of your domain(s):
Code:
<VirtualHost 202.202.202.1:80 202.202.202.2:80>
ServerName mydomain.com
ServerAlias www.mydomain.com
</VirtualHost>
save the configuration and then restart Apache.
NOTE: make a backup of the Apache configuration before making modifications.