To test my Load Balancer I would need to create several TCP/IP connections (from one host). Which tool can be used to create this sessions with different source-ip addresses? (no worries, only in my private LAN).
The easiest thing to do would be to assign multiple IPs to a host, and then use something that lets you bind to specific source IPs. Since this is TCP/IP and you need to handle the response, crafting is probably just a pain.
With linux, you could use Curl for http connections if that is what you happen to be using:
Also with Linux, if you want lower level tcp, you might consider netcat