Yes, the IPv4 gateway is your router. (gateway = router)
You can use your router for Primary DNS.
A lot of people default to Google's DNS servers:
Primary - 8.8.8.8
Secondary - 8.8.4.4
I had this problem as well... it was very frustrating. I'm trying to remember what I did to fix it! I think it may have been to switch on UPnP rather than port forwarding in the router and NVR?