Iperf VIP pointing to iperf running on the same F5

What are you trying to achieve? What is the reason for running iPerf? The reason I ask is F5 has two Operating Systems, TMOS which does your traffic management and load balancing, manages your self IPs and is fine tuned for performance and moving packets quickly. Whereas the Linux operating system, where the Management interface is managed is not as finely tuned and not designed for packet flow.

What you are probably experiencing is an internal routing issue (packets not routing back via VIP but routing internally) Even if you were able to get this to work, because of the distinct OSs, you will not achieve accurate performance statistics through the LTM.