CGN3 keeps rebooting itself

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I'm Here A Lot
Posts: 6

CGN3 keeps rebooting itself

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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Resident Expert
Resident Expert
Posts: 6,147

Re: CGN3 keeps rebooting itself

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.



I'm Here A Lot
Posts: 6

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)
1621000000256QAM3.500438.605
2591000000256QAM5.1001238.605
3597000000256QAM4.6001338.983
4603000000256QAM4.000138.605
5609000000256QAM4.500238.605
6615000000256QAM4.400338.605
7633000000256QAM4.400538.983
8639000000256QAM3.900638.983
9645000000256QAM3.400738.605
10651000000256QAM4.100838.605
11657000000256QAM4.400938.605
12663000000256QAM3.8001038.605
13669000000256QAM3.8001138.605
14675000000256QAM4.4001438.605
15681000000256QAM5.4001538.605
16687000000256QAM5.1001638.605
17693000000256QAM5.6001738.983
18699000000256QAM5.7001838.605
19705000000256QAM5.3001938.983
20711000000256QAM5.7002038.605
Upstream Overview
Port IDFrequency (MHz)ModulationSignal strength (dBmV)Channel IDBandWidth
130596000ATDMA - 64QAM42.00026400000
223700000ATDMA - 64QAM42.00036400000
338596000ATDMA - 64QAM42.50013200000
Resident Expert
Resident Expert
Posts: 6,147

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.

 

 



I'm an Advisor
Posts: 764

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 Amazon.ca and smooth sailing since).

I'm Here A Lot
Posts: 6

Re: CGN3 keeps rebooting itself

Thank you for answering. I'll try to provide answers for all the scenarios you put forward.

 

I live in a house and as far as I know the cable comes from a post outside. When they installed it in October, the tech said that he had to install it from scratch because the job had been botched before. 

 

When I exchanged the modem, I also exchanged the power supply. The modem sits vertically and was plugged directly in the wall. However, the plug was located behind a couch, perhaps limiting its ability to cool off (although it wasn't hot when I touched it). The modem was also located under a surround sound speaker, and I've read people say that perhaps that could cause interference.

 

This morning, I moved the modem to the floor, away from the speaker, and have it plugged directly in the wall, unobstructed. I suppose we'll have to see if that resolves the issue.

 

Fingers crossed!

 

 

I'm Here A Lot
Posts: 6

Re: CGN3 keeps rebooting itself

It did it again tonight, even after relocating the modem. I'm out of ideas.
Resident Expert
Resident Expert
Posts: 6,147

Re: CGN3 keeps rebooting itself

Were you able to log into the modem and see if there was anything unusual about the signal levels?

 

Next step is to isolate the inputs and outputs.   When you look at the modem, there isn't that much that can go wrong, power, ethernet connected devices and cable input. 

 

1.  If you happen to have an extension cord available, I'd use that to plug the modem into a different house electrical circuit.  Run that as a test configuration, looking for a failure.

2.  If you do have a failure, its not a power issue.  In that case, if you have ethernet connected devices, you can either disconnect them as a group altogether, or disconnect them one at a time, looking for a failure after each disconnect.  This might take a few days to work thru. 

3.  Final step would be to disconnect the wifi devices, one network at a time, but first, have a look for power or ethernet caused failures.

 

We have seen what appear to be failures with both CGN3 and CGN3ACSMR.  However, stepping thru a test program has revealed the cause to be a failing ethernet or wifi adapter on the connected device.  However, we haven't seen a reboot occur in all of this, so this is a little unusual.  So, have a go at this to see what happens. 



I'm Here A Lot
Posts: 6

Re: CGN3 keeps rebooting itself

1. I'm not sure I have an extension cord long enough to get to a different room but if I find one I'll try.
2. I have no Ethernet devices connected.
3. You're saying it's possible that one of the clients is making this modem reboot?

By the way, if I look at DOCSIS Event after a crash, there's always this error:
Type: 90000000
Priority: warning
Event: MIMO Event MIMO: Stored MIMO=-1 post cfg file MIMO=-1;CM-MAC=00;CMTS-MAC=00;CM-QOS=1.1;CM-VER=3.0;

Does that help?

I'm Here A Lot
Posts: 6

Re: CGN3 keeps rebooting itself

A tech came in Sunday and tested the connections everywhere, with good results. He did replace a connector outside that he said was loose and could cause the issue I was having. So far so good...