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CM1000 - Another Speed Drop Woe (From Gigabit/900Mbps to 400Mbps to 20Mbps)

Lavarinth
Aspirant

CM1000 - Another Speed Drop Woe (From Gigabit/900Mbps to 400Mbps to 20Mbps)

Hi all. Just posting to see if I can get any assistance with my Netgear CM1000 cable modem. It was purchased in June of 2019, so nearing a two year life in two months. Over the past few months, I would estimate it as the past three months, I noticed I no longer receive my full ISP's speed of "up to 900Mbps". A technician appeared yesterday and tested the lines up to the modem and confirmed the speed is rating at 1100Mbps via his tool connected to the line, with the line quality being solid and no issues. He then connected his device to the modem via ethernet (his own cord) and determined there was a drop in speed of around 800Mbps at the time. This seems consistent with what I would experience for max speed in a day.

 

However, 2-3 times daily now I experience a drop to around 250-400Mbps. And once daily for around two hours the speed will suddenly drop to 8-14Mbps and climb, slowly, back up to 400Mbps over two hours (using various speed test sites to determine this over hours). Each time over the past three nights that this has happened (though it has happened longer as noted) I have contacted my ISP's support chat and they claim everything appears fine on their end. They last night, for the first time, even though the modem is online on my end and showing fully connected their side is showing up as "offline". A reset signal was received, however, and the modem then appeared online on their end but the slow speed still remained.

 

One would think turning the device off and on (either via the 30 second rule, the switch, the outlet, etc) may fix the issue if it was related to the modem. Doing so does not resolve the issue and the slow speed continued for the night regardless of how many times the modem is reset. Eventually, as mentioned, it returns to it normal speed.

 

My tests all revolve around being connecting directly to a single computer, and I have swapped devices and cords to verify it is not a PC network card issue or ethernet cord issue. I am currently at a loss and exploring all options to see about resolving this after my ISP has stated there is nothing more they can do on their end as everything appears normal for them.

 

I have noticed, in the modem's information, that it states the following firmware, which contrasts with Netgear's own info:

(This is for a CM1000, not v2, and not CM1100)

Hardware Version2.02
 
Firmware Version

V6.01.07

However, the knowledge base page for modem firmwares states the latest firmware for my ISP (Cox) to be V3.01.04. Could this pose an issue? https://kb.netgear.com/000036375/What-s-the-latest-firmware-version-of-my-NETGEAR-cable-modem-or-mod...

 

To my understanding, my Event Logs are pretty clean, and I believe (I may be wrong) that my cable connection information shows a pretty stable setup. (Added as attachments.)

Model: CM1000|Ultra-High Speed Cable Modem—DOCSIS® 3.1 Ready
Message 1 of 7
Lavarinth
Aspirant

Re: CM1000 - Another Speed Drop Woe (From Gigabit/900Mbps to 400Mbps to 20Mbps)

This post is to attach my event logs.

Message 2 of 7
FURRYe38
Guru

Re: CM1000 - Another Speed Drop Woe (From Gigabit/900Mbps to 400Mbps to 20Mbps)

Have the ISP check the signal and line quality UP to the modem. Be sure the ISP provisions the modem correctly.
Be sure there are no coax cable line splitters in the between the modem and ISP service box. 
Be sure your using good quality RG6 coax cable up to the modem. 
Be sure to power OFF the modem for 1 minute them back ON.
https://community.netgear.com/t5/Cable-Modems-Routers/General-info-and-Troubleshooting-for-Cable-Mod...

Message 3 of 7
Lavarinth
Aspirant

Re: CM1000 - Another Speed Drop Woe (From Gigabit/900Mbps to 400Mbps to 20Mbps)

Hi there @FURRYe38 thank you so much for the input!

I can thankfully fill in that all those options have checked out per the tech's visit and a follow up call to customer support. I additionally called in after your post to verify if your suggestions and they confirmed these actions were confirmed and all were stable. There are also no splitters as verified by the tech and myself. The cable itself connected to their diagnostic device shows perfect reception of the service.

 

The extremely low Mbps did reappear again tonight and I'm currently typing with a 22Mbps connection versus the expected 800Mbps+. As soon as it hit, I went through with the modem reset as requested of one minute (or more) and the situation did not remedy from this. I did however, copy down the logs that were freshed in case this may be of any assitance. Again, this issue of low Mbps will "resolve itself" after 2-3 hours to a 250-400ish Mbps speed for the remainder of the night until the morning when it occurs again.

 

TimePriorityDescription
2021-04-23, 21:58:56Notice (6)CM-STATUS message sent. Event Type Code: 20; Chan ID: 159; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=3c:37:86:e9:1c:d8;CMTS-MAC=00:aa:6e:c1:05:d6;CM-QOS=1.1;CM-VER=3.1;
2021-04-23, 21:57:32Warning (5)Dynamic Range Window violation
2021-04-23, 21:57:32Warning (5)RNG-RSP CCAP Commanded Power Exceeds Value Corresponding to the Top of the DRW;CM-MAC=3c:37:86:e9:1c:d8;CMTS-MAC=00:aa:6e:c1:05:d6;CM-QOS=1.1;CM-VER=3.1;
2021-04-23, 21:57:32Warning (5)Dynamic Range Window violation
2021-04-23, 21:57:32Warning (5)RNG-RSP CCAP Commanded Power Exceeds Value Corresponding to the Top of the DRW;CM-MAC=3c:37:86:e9:1c:d8;CMTS-MAC=00:aa:6e:c1:05:d6;CM-QOS=1.1;CM-VER=3.1;
2021-04-23, 21:57:32Warning (5)Dynamic Range Window violation
2021-04-23, 21:57:32Warning (5)RNG-RSP CCAP Commanded Power Exceeds Value Corresponding to the Top of the DRW;CM-MAC=3c:37:86:e9:1c:d8;CMTS-MAC=00:aa:6e:c1:05:d6;CM-QOS=1.1;CM-VER=3.1;
2021-04-23, 21:57:32Warning (5)Dynamic Range Window violation
2021-04-23, 21:57:32Warning (5)RNG-RSP CCAP Commanded Power Exceeds Value Corresponding to the Top of the DRW;CM-MAC=3c:37:86:e9:1c:d8;CMTS-MAC=00:aa:6e:c1:05:d6;CM-QOS=1.1;CM-VER=3.1;
2021-04-23, 21:57:31Critical (3)No Ranging Response received - T3 time-out;CM-MAC=3c:37:86:e9:1c:d8;CMTS-MAC=00:aa:6e:c1:05:d6;CM-QOS=1.1;CM-VER=3.1;
2021-04-23, 21:57:31Warning (5)Dynamic Range Window violation
2021-04-23, 21:57:31Warning (5)RNG-RSP CCAP Commanded Power in Excess of 6 dB Below the Value Corresponding to the Top of the DRW;CM-MAC=3c:37:86:e9:1c:d8;CMTS-MAC=00:aa:6e:c1:05:d6;CM-QOS=1.1;CM-VER=3.1;
2021-04-23, 21:57:31Warning (5)Dynamic Range Window violation
2021-04-23, 21:57:31Warning (5)RNG-RSP CCAP Commanded Power in Excess of 6 dB Below the Value Corresponding to the Top of the DRW;CM-MAC=3c:37:86:e9:1c:d8;CMTS-MAC=00:aa:6e:c1:05:d6;CM-QOS=1.1;CM-VER=3.1;
2021-04-23, 21:57:26Notice (6)DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1.;CM-MAC=3c:37:86:e9:1c:d8;CMTS-MAC=00:aa:6e:c1:05:d6;CM-QOS=1.1;CM-VER=3.1;
2021-04-23, 21:57:21Notice (6)TLV-11 - unrecognized OID;CM-MAC=3c:37:86:e9:1c:d8;CMTS-MAC=00:aa:6e:c1:05:d6;CM-QOS=1.1;CM-VER=3.1;
2021-04-23, 21:57:20Warning (5)ToD request sent- No Response received;CM-MAC=3c:37:86:e9:1c:d8;CMTS-MAC=00:aa:6e:c1:05:d6;CM-QOS=1.1;CM-VER=3.1;
2021-04-23, 21:57:20Warning (5)DHCP WARNING - Non-critical field invalid in response ;CM-MAC=3c:37:86:e9:1c:d8;CMTS-MAC=00:aa:6e:c1:05:d6;CM-QOS=1.1;CM-VER=3.1;
Time Not EstablishedNotice (6)Honoring MDD; IP provisioning mode = IPv4
Time Not EstablishedCritical (3)UCD invalid or channel unusable;CM-MAC=3c:37:86:e9:1c:d8;CMTS-MAC=00:aa:6e:c1:05:d6;CM-QOS=1.1;CM-VER=3.1;
Time Not EstablishedCritical (3)SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=3c:37:86:e9:1c:d8;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2021-04-23, 21:53:28Critical (3)No Ranging Response received - T3 time-out;CM-MAC=3c:37:86:e9:1c:d8;CMTS-MAC=00:aa:6e:c1:05:d6;CM-QOS=1.1;CM-VER=3.1;
Time Not EstablishedCritical (3)UCD invalid or channel unusable;CM-MAC=3c:37:86:e9:1c:d8;CMTS-MAC=00:aa:6e:c1:05:d6;CM-QOS=1.1;CM-VER=3.1;
Time Not EstablishedCritical (3)SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=3c:37:86:e9:1c:d8;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
Message 4 of 7
FURRYe38
Guru

Re: CM1000 - Another Speed Drop Woe (From Gigabit/900Mbps to 400Mbps to 20Mbps)

I would ask your ISP to check why the modem is reporting these in the logs:

"Commanded Power Exceeds Value Corresponding" 

Should not be seeing those entries. 

Message 5 of 7
Lavarinth
Aspirant

Re: CM1000 - Another Speed Drop Woe (From Gigabit/900Mbps to 400Mbps to 20Mbps)

Well, their only solution was to have me rent a modem or replace the modem, unsurprisingly, when I pointed out the errors to their support- they claim it to be a malfunction withim the modem itself. The technician that visited prior also claimed modems are "getting more wear and tear thanks to the pandemic", which seemed... like an interesting take.

 

Message 6 of 7
FURRYe38
Guru

Re: CM1000 - Another Speed Drop Woe (From Gigabit/900Mbps to 400Mbps to 20Mbps)

The the rented modem for a month to see if the same thing happens, then you'll know either way. 

Message 7 of 7
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