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CGN3 keeps rebooting itself

I'm Here A Lot

So, intermittently, my CGN3 modem will reboot itself. All the lights, except the power light, shut off and it takes about 3 minutes to come back up. This evening, this happened about 5 or 6 times in the span of 90 minutes. This issue had occured to me before and after speaking with a Rogers tech, the modem was exchanged and no issues were had for about 3 weeks, until this evening. What are the odds of 2 defective modems? The last time this happened, a tech ended up coming after I replaced the modem and tested the signal and said it was very good.


I spoke with tech support again this evening and they're sending another tech but I am skeptical that they'll find anything wrong. Any ideas?


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Accepted Solutions

Re: CGN3 keeps rebooting itself

I've Been Here Awhile


The issue appears to be solved. A technician was sent home, who concluded that there probable was too much noise in the cable feeding the modem. He changed the cable feeding the modem, and the problem appears to have been solved with that.

Thank you!


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Re: CGN3 keeps rebooting itself

Resident Expert

My guess would be that the modem is rebooting in order to regain comms with the neighborhood node.  One modem failure, okay, two, not okay, three, you should be buying lottery tickets.  Can you log into the modem, navigate to the STATUS.... DOCSIS WAN page, copy the downstream and upstream tables and paste them into this thread. Those tables are the RG-6 signal levels which should be of interest at the present time.

Re: CGN3 keeps rebooting itself

Thanks for responding. Here are the tables.


Downstream Overview
Port IDFrequency (MHz)ModulationSignal strength (dBmV)Channel IDSignal noise ratio (dB)
Upstream Overview
Port IDFrequency (MHz)ModulationSignal strength (dBmV)Channel IDBandWidth
130596000ATDMA - 64QAM42.00026400000
223700000ATDMA - 64QAM42.00036400000
338596000ATDMA - 64QAM42.50013200000

Re: CGN3 keeps rebooting itself

Those signal levels and signal to noise ratios look fine.  Only thing I can think of in relation to those levels would be a rapid loss and regain of the cable signals, which might cause the modem to initiate a reboot, but at this time they're fine.   If there was a rapid spike down, I doubt that you would be able to catch it, but, if this does happen again, see if you can log in fast enough after the reboot and have a look at the signal levels to see if there are any big differences.  Are you in a house, and if so, is the external cable leading to the house arriving overhead from a utility pole, or underground from the local tap?


Do you run your equipment from a power bar, and if so, have you tried to run everything with the power bar completely disconnected to determine if the power bar itself is causing the issue.


Can you check the power adapter for the modem and see if it is hot to the touch.  It should only be slightly warm. 


When you replaced the modem, did you replace the power adapter as well?


Is the modem standing upright and is it in a location where it will stay cool, ie, not located within a cabinet.



Re: CGN3 keeps rebooting itself

I have seen something similar - @Datalink touched on it - does your power adapter (running from the modem to wall) feel warm to the touch?


Try plugging it into a different outlet, or different power bar if possible.


In my case, replacing my power bar fixed the issue (it was overloaded and very old, purchased a 12-port Belkin from and smooth sailing since).