Best Practices for IP camera VMS/NVR network setup?

Hi,

I am working with a client who has 30+ IP cameras & was looking to find out of the IP cameras where 'phoning home'. With some advice from another subreddit, I installed Pi-Hole and am able to see that some of the cameras are in fact sending web requests to a few domains.

Before reporting back to the customer, what is the best way to move this forward / lock it down?

They have a PFsense router, a few Cisco layer 2 switches, some IP phones etc.

Everything is setup on a single network (192.168.1.X)

Roughly:

30+ various IP cameras 25+ Cisco IP Phones 20 Workstations/Laptops ? Devices on wifi.

They do have a guest Vlan for wifi traffic (not in this list).

Everything else is all on one IP Range.

Any advice on moving this project forward without over complicating things?

Do I just block (how) the range of IP cameras from internet access (Range 192.168.1.200-192.168.1.235).

Thanks, Rich