Random "Server name or IP"

[Bernhard Wellhöfer]

Hello,
 
I want to test a cluster system with two web frontend server (each with it's 
own IP). How to I randomly set the IP number? What I want is a test plan like
 
Test Plan 
    HTTP Defaults for port, protocol and path
    Randomly a HTTP Defaults to select one of two possible IPs
    HTTP Request
    HTTP Request
 
I already tried a Random Controller with two HTTP Defaults (one for each IP), 
but had no sucess.
 
Who can help me here?
 
Regards,
 
Bernd