Do I need IP spoofing? - Yes, if your system uses IP-dependent load balancing
Scenario without IP Spoofing
The above picture shows how the System Under Test (SUT) is being loaded if we test the application without IP Spoofing. Reason being that all the network elements and the servers have cache and they consider clients IP as the means to route the requests to different tiers, so if we don't have IP Spoofing a LoadGenerator can have only 1 IP and so the path traced by 1 Vuser and the other is the same as seen above as Routers and the Load Balancers will treat that the same user is coming with a new request.
Scenario with IP Spoofing
Performance testing targets are only met if we do the testing the same way as the system is loaded in the real time (same way as shown in the above snapshot) . Every performance test should aim at loading the SUT as shown above and thus highlight the genuine performance bottlenecks.
How do I implement IP spoofing?
1. Run the IP Wizard on each Vuser host machine (Load Generator)
2. Enable the IP Spoofer from the Controller's main menu.
