ClientIPForwarder is a simple ISAPI plug-in for Microsoft ISA server using pass-through technology to control incomming requests on Microsoft ISA server. It modifies http(s) request header and adds variable IPREMOTEADDR containing client IP address to it. It also can map http server variables into your own variables in http header.This plug-in addresses a common problem when your internet asp, php or java application running on internet server behind Microsoft ISA server needs to collect real client IP addresses or other real client variables in http header. Without the plug-in it 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: Variable IPREMOTEADDR and your own variables can be accessed for example by ASP object Request and collection GetServerVariables. ClientIPForwarder was tested on Microsoft Windows 2000 Server SP3 and higher + Microsoft ISA Server 2000 with or without ISA SP1. Nonregistered version of ClientIPForwarder is fully functional but an information message is written into Windows Event Log every 4 hours. It contains short text stating that ISA filter is not registered. It is legal to use nonregistered version for one month for testing purposes.