OK, so the Arris gateway is a digital TV box, is that right?
http://media.datatail.com/docs/specs/140157_en.pdf
So is it the Arris that's connected to the internet? It seems to be a cable modem. Or is it the Netgear (
https://www.netgear.com/home/product...rs/R6900P.aspx) that's connected to the internet?
As I said previously, the double NAT error sounds as if both the devices think they are connected to the internet in series.
There's 2 workable scenarios:
A) The device directly connected to the internet (cable / DSL) needs to be configured as a modem only, with no routing or DHCP functionality - and whichever device is downstream should be connected via its WAN port to the upstream device - the downstream device will do all the firewall / routing / DHCP / WIFI.
B) The device connected to the internet does all the firewall / routing & DHCP functionality - and whichever device is downstream should NOT be connected via its WAN port to the upstream device (just via standard Ethernet switch port), and must have it's routing and DHCP functionality disabled.
My own setup is the former - my ISP-supplied wifi cable router is in modem-only mode, and my own Linksys wifi router is connected to it via the WAN port on the Linksys, which does all the wifi, routing & DHCP.
SD