IP Camera Gateway On Segregated Network

Hey Y’all,
So I’ve recently been promoted to a system programmer position at the security company I work for and I’m looking for some insight on gateways for IP cameras.
On typical installs where we provide all the equipment we usually plug our cameras into a a non-managed PoE switch which plugs into NIC1 of our NVR and then NIC2 of the NVR plugs into the customers switch which makes the NVR the only device on both networks.
In this scenario what should I set the Gateway address of the IP cameras to as they don’t communicate with a router directly? Normally we use the IP address of the NVR but I was wondering if this is technically correct or the best practice. Thanks for any input.