Auto IP setting for R2000 and PC

Hi

I am using 2x Pepperl_fuchs R2000 lidar, and i wish to connect them to the PC (has 6 ethernet ports) directly. I read the manual, if i set it to link locally, the 2d lidars will be auto assigned with IP address. But how to ensure the IP-address for both units are fixed for using Auto-IP? So that i dont have to configure it everytime when boot up.

Best,
Samuel