Thanks David for your reply.
Here is my router info
Tenda HG9 Dual-band - Main Router
Dlink Wireless AC1200 - configured as wifi extender
Not using VLAN. I wanted to make it in a single subnet
I have 5 Wifi Outdoor cameras ( EZVIZ C3TN) and - 8 Channel Ezviz NVR (X5S-8W) with Harddisk for local storage.
My internet router is directly connected to NVR with Ethernet.
2 Cameras directly connected to NVR Wifi Network
3 Camera connected to Wifi Extender Network from the Main Router.
All...