(Owncloud) IP changes after reboot

I have a weird issue. After I setted up my Owncloud account, I received address http://192.168.0.107 however after reboot/restart it changed to http://192.168.0.103 and I can not login even with default password. (btw I already used and uploaded some files to 192.168.0.107)

The answer I received in Owncloud forum was (quote): you have configured the Univention Networking using DHCP, and if the IP is changing always in every restart, verify your DHCP Server and verify the configurations and/or add a fixed address rule for your univention machine.

Where I can find these settings?
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