mod_limitipconn is an Apache which allows web server administrators
to limit the number of simultaneous downloads permitted from a single
IP address.

You'll need to add the following line to your /etc/httpd/httpd.conf:
  Include /etc/httpd/mod_limitipconn.conf

To test the 'test.pl' utility from mod_evasive is included in the doc dir.
Which when run multiple simultainus sessions of should similate accessive
connectivity; e.g. with MaxConnPerIP set to ``1'' 
  while true; do (perl ./test.pl &); perl ./test.pl; done