Spectrum Wave 2 modem (Hilton EN2251) does not assign an IP to my own router
I was on a 300 Mbps plan with an Arris DG1670A modem/wifi-route all-in-one.
Recently, I upgraded to 400 Mbps. The Spectrum saleswoman told me that she couldn't let me use the old modem and must send me a new modem and a new wifi-route. I asked for just the modem as I have an excellent spare wifi-route, but she didn't see the modem-only option. So, I was forced to pay the $5/month for the wifi-router.
I received an Hiltron EN2251 modem and an Askey SAC2V1K wifi-router. Then, the nightmare began.
By default, the SAC2V1K sets up the LAN subnet 192.168.1.xxx, but I have a dozen of devices preset to 192.168.0.xxx, which I don't intend to change. The Spectrum App is the only oversimplified GUI to make changes, and it does not allow me to change the subnet IPs.
Swapping the SAC2V1K to my own wifi-router does not work because the Spectrum modem does not assign an IP to it. Manually setting 192.168.0.2 (wifi-router) / 192.168.0.1 (gateway) or 192.168.100.2 (wifi-router) / 192.168.100.1 (gateway) did not give me any Internet access. (Note, though, in the latter setup, I could successfully ping 192.168.100.1, but still no setup GUI or Internet.)
I wonder if there is a way to either change the subnet on the Spectrum wifi-router or use my own router. If I should get a different modem model, I'd be happy to go to the store too. Thanks!