Dahua nvr 16 integrated poe switch

Hello allo :

I have two nvr dahua 16 poe integrated switch and 30 caméra dahua poe,i reset them and i assigne IP adress for nvr 192.168.1.10 and 192.168 .1.11,
For caméra dahua i assigne 10.1.1.100 to .130.
But why when i restart NVRs ,they restore IP adress from 10.1.1.65 to incrément value to 66 and 67 ....etc.?
Thanks for your supporr