Router and modem compatability

[Lzrosenberg]

We have a Nighthawk AX8 router. We recently upgraded to one gigabyte Speed through Comcast. We purchased the net gearCM1200 modem.

When we plug the router directly into the modem, The Internet symbol stays red, and will not turn white.

Does anyone have a suggestion?

Thanks, Laurence

[myersw]

Since the modem is brand new never been used according to your post, the first thing is to determine if the modem is defective. According to the manual, do the lights appear correct on the modem? If not contact your ISP for further problem determination.

One way to test is to connect a PC/MAC via Ethernet to the modem and see if you get a connection and access to the Internet. If so then issue is with getting the modem and router talking to each other which would require doing things in the correct order. 

Power off both modem and router.

Next power up just modem and wait until it has stablized, 2 -5 minutes.

Next power up the router

Should be able to connect modem to router and get Internet at this time. 

[plemans]

another thing to check, the cm1200 has 4x ethernet ports. Unless you're on a business class line with comcast/pay for multiple ip address, you can only use port 1 (or 1&2 if you have a router that supports port aggregation on the wan port). Make sure nothing else is plugged into the modem.  

Otherwise agree with everything @myersw said.