Re: Netgear CM1100 Continually Rebooting

Scott911 · ‎2019-12-28

Hi, I have had a rough time with a New CM1100 i bought from Costco. I have Spectrum and once the modem was installed and activated it started rebooting every 2-3 minutes and was not functional. I returned it to Costco and got another one. Same issue, the Spectrum techs said it was the modem and not thier service. I have no idea what to do, so hooked up the old Asus modem and it works. I am using the Nighthawk AX8 router and wanted to use a Netgear Modem, but now I don't know what to do. Any ideas on what modem I can use. Spectrum is going to DOCSIS 3.1.

Any suggestion would be great.

WmartCustomer · ‎2019-12-28

Well could be someone nearby is attacking your network with Reaver or some other wifi sniffing tools. Or like the warnings currently on netgears site about buffer overflow sort of attack happening which could be from the internet side too. It could be something searching for that specific stack overflow flaw and trying to exploit it.

Can be other signals in house. Depends on what its normally connecting with. 2.4 spectrum is cordless phones which can interrupt wifi frequencies. Whatever the cause its odd that both produce the same results.

plemans · ‎2019-12-28

check your connection settings. if your power is to high, it can cause reboots.

You can pull them off your current modem.

Post them here so we can see what your old modem is running.

If there's an amplifier in line, remove it. and reconnect the modem. If it doesn't work and the power is indeed high, put a splitter (I usually have people remove splitters) in line and reconnect. If the power is to high, a splitter can reduce it potentially enough to run decent.

If the power is low, we'll have you remove splitters, attenuators, amplifiers from the line.

the current modem you're running will at least give us a rough idea of your power levels.

Spectrum is natorious for refusing to do anything if the modems aren't their own. I've had to actually rent/use one of their modems for a month to prove to them it was their line causing issues.

Scott911 · ‎2019-12-30

Attached is my Modem data. I am using a Asus CM-16 as I had to remove the Netgar CM1100 for the network to work.

Thanks for the assistance

plemans · ‎2019-12-30

You've got line issues. You've got errors on your incoming line with it being a bit high and your upstream strength is way to low. Minimum is 35 dBmV with 45 dBmV being ideal for upstream. Probably why the CM1100 wouldn't connect as it needs a decent upload.

I'd have your ISP check your line.

Scott911 · ‎2019-12-31

Thanks - I will call spectrum. I wonder if the splitter can help? The splitter is a Extreme BDS103H and 5-1002 MHZ, and the modem is connected to the -7db, maybe I should try the -3.5db?

plemans · ‎2019-12-31

First thing I'd do is move the modem to right where the line enters the house. directly connect there with no splitters.

Then check your power levels. and post them here.

A bad splitter/cheap splitter/etc can cause all kinds of issues.

If you're running cable tv and a modem it should always go incoming line-------double splitter with one lead to modem and another to either to a tv or another splitter for your tv. for the time being, remove all splitters and see what happens with the signal.

TheRealSpinner · ‎2020-06-14

I am having the same rebooting problems with my brand new Netgear CM1100 (Costco) Cable Modem.

A year ago I purchased the Netgear CM1000 Cable Modem from Costco. I was going to replace my Netgear CM600 which is rock solid with Cox Communications. Purchased the CM1000 to get Gigablast. This ended up in failure. CM1000 would not keep connection kept rebooting. Cox Technician came out and replaced part at the Node across my street. Tried to get a stable connection with CM1000 no luck kept rebooting. I gave up and went back to the CM600 (Rock Solid).

Purchased the CM1100 after returning the CM1000. Decided to give it another shot with the New Netgear CM1100 and Cox Communications. Same crap is happening again. CM1100 is rebooting again and again. Gave up again and went back to CM600 (Rock Solid). Cox Technician is coming out Wednesday.

What could be the problem?

I do have an old splitter that Cox Communications installed in my attic that splits the coax cable (from outside of house) to existing coax outlet in office and to coax outlet in closet where all network equipment is installed. Cable Modem, Router, Switches, etc.

I have attached an image of my existing Netgear CM600.

Any help would be appreciated.

FURRYe38 · ‎2020-06-15

Would need to see same singal capture with CM1100 connected.

I would remove splitter.

Have ISP tech try one of there modems to see if there modem does same thing or not.

@TheRealSpinner wrote:
I am having the same rebooting problems with my brand new Netgear CM1100 (Costco) Cable Modem.

A year ago I purchased the Netgear CM1000 Cable Modem from Costco. I was going to replace my Netgear CM600 which is rock solid with Cox Communications. Purchased the CM1000 to get Gigablast. This ended up in failure. CM1000 would not keep connection kept rebooting. Cox Technician came out and replaced part at the Node across my street. Tried to get a stable connection with CM1000 no luck kept rebooting. I gave up and went back to the CM600 (Rock Solid).

Purchased the CM1100 after returning the CM1000. Decided to give it another shot with the New Netgear CM1100 and Cox Communications. Same crap is happening again. CM1100 is rebooting again and again. Gave up again and went back to CM600 (Rock Solid). Cox Technician is coming out Wednesday.

What could be the problem?

I do have an old splitter that Cox Communications installed in my attic that splits the coax cable (from outside of house) to existing coax outlet in office and to coax outlet in closet where all network equipment is installed. Cable Modem, Router, Switches, etc.

I have attached an image of my existing Netgear CM600.

Any help would be appreciated.

Thanatos69 · ‎2020-06-15

Hello -

I'm also having problems with a CostCo purchased cable modem.

I bought one last week, it worked great for a week - then it started to power cycle over and over for about 30 minutes.

I returned it and got a new one from CostCo.

I had it for a day before it started to power cycle for about 30 minutes when I needed to be on a call.

My set up is CM1100 ---> RAX75 ---> switch for my internal network.

I have a network cable hanging off of the RAX75 so I can plug it into different devices when I need to.

Tonight I plugged it into my laptop which should not be issue, and when I was trying to connect to the internet, the CM went on 30 minute cycle.

If the Laptop is connected to the RAX75 why should the CM1100 take a dump??

Attached is my power settings from my modem.

Last week, I had a splitter on my internet connection before it went crazy...

this week, I removed the splitter, and with the new one it still freaked out.

Any and all info is appreciated.

Thanks

TheRealSpinner · ‎2020-06-19

Another Attachment

TheRealSpinner · ‎2020-06-19

Another Attachment

TheRealSpinner · ‎2020-06-19

Another Attachment

plemans · ‎2020-06-19

Your upstream is to low. It can cause frequent drops.

have you had your isp check your line?

TheRealSpinner · ‎2020-06-19

I gave up. Returned Netgear CM1100 to Costco for Full Refund.

Update 06/17/2020:

Cox Technician came out to house around 8:00 AM wasn't able to help me at all.

I DO NOT have a splitter in my attic. Straight Coax Cable from outside Cox box to Coax Outlet in Office.

Called Cox Support again and got moved up to Tier 2? He was able to see Packet Loss which is causing the Netgear CM1100 to reboot. He setup Cox Technicians to come out to my house. They arrive around 5:30 PM. Three Cox Technicians arrived at my house and they were excellent. They knew what to test and how to test for issues.

They ran a new line from my house to Cox Node across the street. For thirty minutes the CM1100 was stable but, after that the cable modem just started rebooting over and over again. I had to go back to trusty Netgear CM600.

Yes, the only line that hasn't been tested would be from the outside cox box to coax outlet in office. If there was a problem with that cable wouldn't I see issues on my CM600?

TheRealSpinner · ‎2020-06-19

For some reason this forum deleted my original post.

TheRealSpinner · ‎2020-06-19

*Recommended Upstream signal levels are +35 dBmV to +49 dBmV (DOCSIS 3.1)

plemans · ‎2020-06-19

And those are just snap shots. The dbmv changes throughout the day.

FURRYe38 · ‎2020-06-19

If the techs changed out everything and was good on there side, sounds like the CM modem may have been just faulty.