Using cable modem and cable wireless modem router?

In this situation, the Netgear can only be used as a wireless AP/switch, it can't route because the WAN (which is normally exposed when using a separate modem and router) is internal. So all you can do is use its switch and/or AP.

You would assign the Netgear a static IP from the same network as the HN9000 (and not in use elsewhere (e.g., the DHCP server of the HN9000), so if the HN9000 is say 192.168.1.1, perhaps make the Netgear 192.168.1.2), disable its DHCP server, and connect them LAN to LAN.

Whether that provides any appreciable benefit, well, that's up to you to decide.

Eibgrad: Thanks so much for the response. I'm not sure, however, what most of it means.
I'm interested in having wifi in the home, and I now have Hughesnet, using the HN9000 connected to a pc. I have a wireless modem/ router (the CG3000d) leftover from having Charter service.

Since I previously got wifi with the CG3000d with Charter, I was hoping somehow I could use it as a router now. Not sure what it being only a switch and/or AP means. Would that provide wifi?

Yes, as I described the necessary changes, you'd now have a wireless AP (access point) on your otherwise wired-only network. And a few more wired (LAN) ports for your wired devices. But ultimately your HN9000 would continue to do all the routing.

[hn9000 - 192.168.1.1](lan)<-- wire -->(lan)[cg3000d - 192.168.1.2, dhcp disabled]<-- wired/wireless -->[wired/wireless devices]

I'm only using the 192.168.1.x network as an example, your HN9000 may use something different (e.g., 192.168.0.x, 192.168.254.x). Adjust accordingly.

OK...sounds promising. Not sure how to assign the Netgear a static IP and disable its DHCP server. How do I do that? Anywhere to go to to read up on how to do this?