To change the IP, you have to connect to the serial port of the controller (power supply rear side). 
A USB adapter is somewhere in the cabinets on 3U, most likely close to the laser service notebook. 
Baud rate is 115200. 
After a restart of the controller, you have 3 seconds to send enter. 
With the command "show" you can see the current configuration. 
To change the ip, you send "ip=192.168.29.51;". Same syntax as shown, including the semicolon at the end. 
Maybe you have also to adjust the gate etc. 
When done, you leave the configuration by sending exit.