RailControl supports all Z21 that are allowed to communicate on LAN.
The standard configuration of the Z21 has the IP address 192.168.0.111 set. If the Z21 is operating on the designated router no more settings are needed. In RainControl one has to configure the IP address 192.168.0.111.
Configuration of the Firewall
Usually there is no special configuration of the firewall needed. If, then a UDP connection to the port 21105 of the Z21 has to be allowed.