When TESTING using Web and WinSocket protocols, by default Vusers on each host machine use the host's (agent's) IP address. Since a particular server keeps serving a specific IP address, load tests would reflect network router caching and other optimizations RATHER than the real-life situation where different users ARRIVE to the server with different IP addresses. This is especially needed when the hardware configuration under test balances load across a "farm" of SEVERAL (web or database) servers. "IP spoofing" enables each host machine to "spoof" the server into thinking it is using many different IP addresses.

When testing using Web and WinSocket protocols, by default Vusers on each host machine use the host's (agent's) IP address. Since a particular server keeps serving a specific IP address, load tests would reflect network router caching and other optimizations rather than the real-life situation where different users arrive to the server with different IP addresses. This is especially needed when the hardware configuration under test balances load across a "farm" of several (web or database) servers. "IP spoofing" enables each host machine to "spoof" the server into thinking it is using many different IP addresses.