Good day to all. Sorry for the late reply.
The ISP modem is fully bridged and DHCP is disabled. As for the QOS, just set the cameras and NVR in the highest priority. For the IP reservation, I set it but to no avail. All connected ate getting fixed end date as indicated in my ipconfig result. Let's say if DHCP is enabled on ISP modem where the WAN side of DIR-880L is connected, will it affect the leasing period considering different subnet with 255.255.255.0 on both WiFi router and modem? Thanks.