Giving access to CCTV cameras


-Main building - 32 cameras / hikvision / running on seperate CCTV POE switch /
-Sub Unit - 8 cameras / dahua / POE cameras /Has their own internet

We have a site which is a serviced office building. It has pfsense running all the CCTV equipment running on an isolated VLAN

The sub unit wants access to some of the hikvision cameras running on the
Most NVRS have 2 subnet networks i understand this and how to add the camera etc.

I am not sure how best to set this up on the network side. If i set up the sub unit with the same subnet as i will be able to add the cameras by linking the 2 networks but this would cause a DHCP conflict and a security concern. I only want the subunit to access the camera IPs i decide.

Does anyone know how to best handle this?

thank you