Re: CM1200 issues with Xfinity ISP and Google Wifi Router

triplea333 · ‎2020-04-26

I have Xfinity as ISP and I'm trying to ditch their Xfi (modem/ router) and cut the monthly rental fee but I'm having the hardest time trying to set up my google wifi routers to it. It continues saying the modem and router must be restarted. I've gone online and researched forums (not really much written on this model). I tried everything with the original Xfi router and it worked so it must be something with my CM1200. PLEASE HELP!

plemans · ‎2020-04-27

did you get it activated?

Was your isp able to see it?

Once activated, log into it and take a screen snip of your modem connections page.

Make sure you only have 1 device connected to the cm1200. It does have 4 ports but the average use can only use 1 port.

FURRYe38 · ‎2020-04-27

Review the user manual on getting a wifi router connected. Also review the user manual for your mfr wifi router as well.

@triplea333 wrote:
I have Xfinity as ISP and I'm trying to ditch their Xfi (modem/ router) and cut the monthly rental fee but I'm having the hardest time trying to set up my google wifi routers to it. It continues saying the modem and router must be restarted. I've gone online and researched forums (not really much written on this model). I tried everything with the original Xfi router and it worked so it must be something with my CM1200. PLEASE HELP!

triplea333 · ‎2020-04-27

I have done that multiple times, reset everything and tried again from scratch and nothing.

triplea333 · ‎2020-04-27

I did get it activated.

My ISP sees it.

See screenshots attached of modem connections.

I only connected the google nest router to it; although I'm not sure why I would not be able to use all 4 ports of it - for that I would have just gone for the CM1100 which has only one ethernet port.

Your help is very much appreciated.

triplea333 · ‎2020-04-27

2nd screenshot attached

plemans · ‎2020-04-27

Your levels look pretty good. and the connect seems fine.

Reason you can't use all 4 ports is a little more complex. I'll try and hit the key points.

A modem isn't a router. it doesn't handle dhcp assignments. It gets a single IP address from the isp (for most isp's). It can use that address to do port aggregation between ports 1-2 if your router supports this. (google mesh doesn't)

It can use the other ports if your ISP supports multiple public ip addresses. Most ISP's (comcast/cox/spectrum) don't support this for consumers. Some of their business class services do.

I'd have to agree that for the vast majority of consumers, the CM1000 or CM1100 would be the best choice. Companies don't do a good job of explaining this and we run into it a lot in the forums.

Does the modem work if you go CM1200------>PC?

Make sure anytime you change which device is connected to the modem that you reboot it like this:

power off the modem and router

power on modem with nothing connected. give it a few minutes to fully boot.

connect device to modem

power on device (router/pc). give them time to fully boot.

Try resetting the google mesh back to factory (in case an old setting is causing an issue) for setup.

FURRYe38 · ‎2020-04-27

Be sure you are connecting the host router to LAN port#1 on the CM1200 modem.

Swap LAN cables between the CM modem and host router with a known working cable. CAT6 is recommended.

LAG should be disabled on the CM modem.

triplea333 · ‎2020-04-27

The modem does work straight into my PC.

I contacted Google Support and they said the routers are working fine but they're not getting an IP or internet access. They told me to contact Netgear for help on setting up DMZ in the modem.

Do any of you know how to do that?

plemans · ‎2020-04-27

There isn't really anything to change on that modem other than link aggregation or login password.

Make sure link aggregation is off.

Make sure the cable going to the google device is working properly.

If the modem is working directly connected to a pc, the modem works fine. They're basically set and forget type devices.

Do you have an old router you could try?

Is the google mesh on its latest firmware?

FURRYe38 · ‎2020-04-28

The CM modem doesnt' have a DMZ since there is no router built in. IF your PC is working connected directly to the CM modem, and if there router isn't, the problem is with there router.

Probably not the LAN cable either if you used the same cable to connect the PC to.

Try a different router to connect to LAN port#1.

@triplea333 wrote:
The modem does work straight into my PC.
I contacted Google Support and they said the routers are working fine but they're not getting an IP or internet access. They told me to contact Netgear for help on setting up DMZ in the modem.
Do any of you know how to do that?

improsiafan · ‎2020-06-15

I had the same issue as the original post and was able to resolve it by following @plemans' advice, below. While I'd thought I was taking those steps previously, turns out that I'd been trying to connect both my Google Wifi router AND the laptop to the CM1200 at the same time. Once I disconnected both devices, then started over following these steps below, the issue resolved. I'm relieved I didn't have to factory reset my Google Wifi.

@plemans wrote:
Make sure anytime you change which device is connected to the modem that you reboot it like this:
power off the modem and router
power on modem with nothing connected. give it a few minutes to fully boot.
connect device to modem
power on device (router/pc). give them time to fully boot.