I have my NeoLoad controller in one side and the load generators in the other side of the firewall. I can open one or two ports but only on one side.
NeoLoad can use multiple load generators to generate the load. In fact, it is recommended so the bottleneck is not the load generator.
By default, the Controller will discover the load generators either automatically or by using the IP address of the load generators. It will connect to port 7100.
This can be an issue on secure environments when you have a firewall between the controller and load generators. Since NeoLoad 4.0, this behavior can be modified so the communication is initiated from the load generators Agent to the controller using port TCP 4569 in controller side.
For more information, see “Advanced Installation” section in NeoLoad documentation.