ClientIPForwarder is a simple ISAPI plug-in for Microsoft ISA server 2000/2004 that uses pass-through technology to control incoming requests on Microsoft ISA server. ClientIPForwarder modifies http(s) request header and adds a variable IPREMOTEADDR containing client IP address to it. . It also can add a content to a http variable or creating new variable or replace an existing http server variable content with a new one. It allows to monitor real client IP addresses in your asp or java application behind Microsoft ISA server. Without the plug-in your application can only access ServerVariables.REMOTE_ADDR (or REMOTE_HOST) containing IP address of ISA firewall. Variable IPREMOTEADDR can be accessed for example by ASP object Request and collection GetServerVariables:

response.write("HTTP_IPREMOTEADDR:" & Request.ServerVariables("HTTP_IPREMOTEADDR:"))

Fully functional trial version free.