CM1200 Modem Dropping Connection

[bcooper27]

Just recently installed the Netgear CM1200 modem to support the 1G Internet service I upgraded to from my ISP "RCN" here in Pennsylvania. I also have an RAX70 Netgear Nighthawk (also new) attached and both are brand new. I've had 2-3 instances of dropped connections on my CM1200 over the last week since I installed it. Both times the DOWNSTREAM light on the modem was just flashing green and we had no service in the house. Both times I turned off the modem by using the power button, kept it off for a minute, turned it back on.  And both times within a minute or so the modem would eventually go all green solid lights and we'd hear the pings on our equipment that the Internet service was back on.

I did read other posts that some people have had the same issue.  I read some said to check wiring, splitters, etc.  Note that this is an upgrade from our previous setup which was a CM600 Netgear Modem with a Netgear Nighthawk X8 R8500 which both worked flawlessly when we had the 250M Internet service from RCN. So the wiring is not an issue.

Below are the event logs from the issue last night.  If anyone has any suggestions I would appreciate it.  Obviously I want to make this work but I can't afford to continue manually resetting the modem to get things up and working every time. It shouldn't be that way. Thanks in advance. - Brian

Time	Priority	Description
Fri Jan 22 11:28:26 2021	Warning (5)	REG-RSP-MP Mismatch Between Calculated Value for P1.6hi Compared to CCAP Provided Value;CM-MAC=08:36:c9:a4:46:d8;CMTS-MAC=2c:0b:e9:14:b0:e9;CM-QOS=1.1;CM-VER=3.1;
Fri Jan 22 11:28:24 2021	Notice (6)	DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=08:36:c9:a4:46:d8;CMTS-MAC=2c:0b:e9:14:b0:e9;CM-QOS=1.1;CM-VER=3.1;
Fri Jan 22 11:28:19 2021	Notice (6)	TLV-11 - unrecognized OID;CM-MAC=08:36:c9:a4:46:d8;CMTS-MAC=2c:0b:e9:14:b0:e9;CM-QOS=1.1;CM-VER=3.1;
Fri Jan 22 11:28:19 2021	Error (4)	Missing BP Configuration Setting TLV Type: 17.9;CM-MAC=08:36:c9:a4:46:d8;CMTS-MAC=2c:0b:e9:14:b0:e9;CM-QOS=1.1;CM-VER=3.1;
Fri Jan 22 11:28:19 2021	Error (4)	Missing BP Configuration Setting TLV Type: 17.8;CM-MAC=08:36:c9:a4:46:d8;CMTS-MAC=2c:0b:e9:14:b0:e9;CM-QOS=1.1;CM-VER=3.1;
Fri Jan 22 11:28:19 2021	Error (4)	Missing BP Configuration Setting TLV Type: 17.7;CM-MAC=08:36:c9:a4:46:d8;CMTS-MAC=2c:0b:e9:14:b0:e9;CM-QOS=1.1;CM-VER=3.1;
Fri Jan 22 11:28:19 2021	Error (4)	Missing BP Configuration Setting TLV Type: 17.6;CM-MAC=08:36:c9:a4:46:d8;CMTS-MAC=2c:0b:e9:14:b0:e9;CM-QOS=1.1;CM-VER=3.1;
Fri Jan 22 11:28:19 2021	Error (4)	Missing BP Configuration Setting TLV Type: 17.5;CM-MAC=08:36:c9:a4:46:d8;CMTS-MAC=2c:0b:e9:14:b0:e9;CM-QOS=1.1;CM-VER=3.1;
Fri Jan 22 11:28:19 2021	Error (4)	Missing BP Configuration Setting TLV Type: 17.4;CM-MAC=08:36:c9:a4:46:d8;CMTS-MAC=2c:0b:e9:14:b0:e9;CM-QOS=1.1;CM-VER=3.1;
Fri Jan 22 11:28:19 2021	Error (4)	Missing BP Configuration Setting TLV Type: 17.3;CM-MAC=08:36:c9:a4:46:d8;CMTS-MAC=2c:0b:e9:14:b0:e9;CM-QOS=1.1;CM-VER=3.1;
Fri Jan 22 11:28:19 2021	Error (4)	Missing BP Configuration Setting TLV Type: 17.2;CM-MAC=08:36:c9:a4:46:d8;CMTS-MAC=2c:0b:e9:14:b0:e9;CM-QOS=1.1;CM-VER=3.1;
Fri Jan 22 11:28:19 2021	Error (4)	Missing BP Configuration Setting TLV Type: 17.1;CM-MAC=08:36:c9:a4:46:d8;CMTS-MAC=2c:0b:e9:14:b0:e9;CM-QOS=1.1;CM-VER=3.1;
Fri Jan 22 11:28:18 2021	Warning (5)	DHCP WARNING - Non-critical field invalid in response ;CM-MAC=08:36:c9:a4:46:d8;CMTS-MAC=2c:0b:e9:14:b0:e9;CM-QOS=1.1;CM-VER=3.1;
Time Not Established	Notice (6)	Honoring MDD; IP provisioning mode = IPv4

[plemans]

do you also have a screen snip of the cable connections page? that helps in conjunction with the logs. 

[bcooper27]

Well I've tried twice to add the Cable Connection snippet and twice my post disappears. Any other way to add this?

[plemans]

Click on "choose file" when adding. You'll only be able to add one at a time. 

[bcooper27]

Lets try this.  See attached pdf.

[FURRYe38]

NOt all your down channels are locked in. For a 1G service you should be getting all 31 or 32 channels lock in. Something to check with the ISP about.

Heres mine:

Startup Procedure

Procedure Status Comment Acquire Downstream Channel 837000000 Hz Locked Connectivity State OK Operational Boot State OK Operational Security Enabled BPI+ IP Provisioning Mode Honor MDD honorMdd(4)

Downstream Bonded Channels

Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables 1 Locked QAM256 31 837000000 Hz -2.5 dBmV 37 dB 0 0 2 Locked QAM256 2 657000000 Hz -2.4 dBmV 36.5 dB 0 0 3 Locked QAM256 3 663000000 Hz -2.2 dBmV 36.6 dB 0 0 4 Locked QAM256 4 669000000 Hz -2.1 dBmV 36.6 dB 0 0 5 Locked QAM256 5 675000000 Hz -2 dBmV 36.6 dB 0 0 6 Locked QAM256 6 681000000 Hz -1.8 dBmV 36.8 dB 0 0 7 Locked QAM256 7 687000000 Hz -1.7 dBmV 36.8 dB 0 0 8 Locked QAM256 8 693000000 Hz -1.5 dBmV 36.8 dB 0 0 9 Locked QAM256 9 699000000 Hz -1.3 dBmV 37 dB 0 0 10 Locked QAM256 10 705000000 Hz -1.3 dBmV 36.8 dB 0 0 11 Locked QAM256 11 711000000 Hz -1.2 dBmV 36.9 dB 0 0 12 Locked QAM256 12 717000000 Hz -0.7 dBmV 37.1 dB 0 0 13 Locked QAM256 13 723000000 Hz -0.8 dBmV 36.9 dB 0 0 14 Locked QAM256 14 729000000 Hz -0.7 dBmV 36.9 dB 0 0 15 Locked QAM256 15 735000000 Hz -0.5 dBmV 37 dB 0 0 16 Locked QAM256 16 741000000 Hz -0.5 dBmV 37.1 dB 0 0 17 Locked QAM256 17 753000000 Hz -0.6 dBmV 37.1 dB 0 0 18 Locked QAM256 18 759000000 Hz -0.8 dBmV 37.1 dB 0 0 19 Locked QAM256 19 765000000 Hz -1.2 dBmV 37.1 dB 0 0 20 Locked QAM256 20 771000000 Hz -1.2 dBmV 37.2 dB 0 0 21 Locked QAM256 21 777000000 Hz -1.4 dBmV 37.3 dB 0 0 22 Locked QAM256 22 783000000 Hz -1.6 dBmV 37.3 dB 0 0 23 Locked QAM256 23 789000000 Hz -1.7 dBmV 37.3 dB 0 0 24 Locked QAM256 24 795000000 Hz -1.8 dBmV 37.3 dB 0 0 25 Locked QAM256 25 801000000 Hz -2 dBmV 37.1 dB 0 0 26 Locked QAM256 26 807000000 Hz -2 dBmV 37.2 dB 0 0 27 Locked QAM256 27 813000000 Hz -2.1 dBmV 37.2 dB 0 0 28 Locked QAM256 28 819000000 Hz -2.5 dBmV 37 dB 0 0 29 Locked QAM256 29 825000000 Hz -2.3 dBmV 37.2 dB 0 0 30 Locked QAM256 30 831000000 Hz -2.4 dBmV 37 dB 0 0 31 Locked QAM256 32 843000000 Hz -2.5 dBmV 37 dB 0 0 32 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0

Upstream Bonded Channels

Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power 1 Locked ATDMA 1 5120 Ksym/sec 36000000 Hz 39 dBmV 2 Locked ATDMA 2 5120 Ksym/sec 29000000 Hz 37.8 dBmV 3 Locked ATDMA 5 5120 Ksym/sec 22000000 Hz 38.3 dBmV 4 Locked ATDMA 6 2560 Ksym/sec 16000000 Hz 37 dBmV 5 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 6 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 7 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 8 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV

Downstream OFDM Channels

Channel Lock Status Modulation / Profile ID Channel ID Frequency Power SNR / MER Active Subcarrier Number Range Unerrored Codewords Correctable Codewords Uncorrectable Codewords 1 Locked 0 ,1 ,2 33 547000000 Hz -4.0 dBmV 36.6 dB 1108 ~ 2987 713286238 549483486 9 2 Not Locked 0 0 0 Hz 0 dBmV 0.0 dB 0 ~ 4095 0 0 0

Upstream OFDMA Channels

Channel Lock Status Modulation / Profile ID Channel ID Frequency Power 1 Not Locked 0 0 0 Hz 0 dBmV 2 Not Locked 0 0 0 Hz 0 dBmV

[bcooper27]

My ISP RCN tech told me tonight in the 2-3 years he’s handled troubleshooting 1G service he’s only ever seen 16-channels locked. He thinks it’s an issue with the equipment itself. He saw no drop issues overnight when I lost service so he thinks possible bad modem.

[plemans]

But you've also only got 2 locked upload. it could be a bad unit. Nothing is saying it isn't but my channels lock the same as @FURRYe38 and I'm on a 1 gig line. 

[FURRYe38]

I would presume this tech should know that for any 1Gb service, at least here in the US region, 32 is the norm for this speed service. If there not seeing anything liek this, there it's either there signal that needs to be check into or of course could be bad modem HW. I beleive the DOCSIS spec uses 31-32 channels for 1G service lines. Unless some ISP has figured out how to compress a 1Gb service line to 16 channels...would be doubtful though....

Try another modem and see if the problem follows or not.

---

@bcooper27 wrote:
My ISP RCN tech told me tonight in the 2-3 years he’s handled troubleshooting 1G service he’s only ever seen 16-channels locked. He thinks it’s an issue with the equipment itself. He saw no drop issues overnight when I lost service so he thinks possible bad modem.

---

[bcooper27]

I chatted with another RCN rep who insisted everything was fine. I told them I wanted it escalated to their tech group to have this looked at and they said I’ll get an answer in a few days. I have a Nighthawk AX8 RAX70 attached to the modem and my speed tests do hit 850-890Mbps. Still think something is wrong here considering everyone’s responses. I’ll get to the bottom of it.

[bcooper27]

First I appreciate the help and responses. Still trying to narrow down this issue as I await RCN’s technical team to look into this. So this morning at 6:58am the modem dropped service again. Do the attached Event Logs lead anyone to a possible issue? This techy modem jargon is just Greek to me.

[bcooper27]

2nd attachment.

[FURRYe38]

Lots of Errors in there. Thats needs to be reviewed and addressed by the ISP/Tech. Have them look at this log and your connection status page. It should be similar to mine:

https://community.netgear.com/t5/Cable-Modems-Routers/CM1200-Modem-Dropping-Connection/m-p/2044114/h...

[bcooper27]

I've scheduled an RCN Tech to be onsite on Thursday 1/28.  Hopefully I'll get some answers about this modem dropping issue (which is still occurring 1-2 times every day) and will let you all know how it goes.  

[FURRYe38]

Also have the tech look at the modems UI and watch you speed test as well with a wired PC connected to the modem while he's there. 

[bcooper27]

One other bit of info from RCN.  I reached out to them via Twitter and they sent the question about the 32-channels to their technical group.  Here's their answer:

"We use whatever channels we need to use to accomplish the needed speed. If pressed, for RCN, we usually shift into OFDM channels after 16, though this can vary."

[bcooper27]

RCN Technician came by today.  He initially checked the signal on the cable in my office to check for errors and all looked good...no issues. He checked the connections outside my home and found the connection at the pole and the connections on either side of the underground cable were 'bad.' He also said there was a splitter on the outside of the home that didn't need to be there. She he replaced all the connections and took out the splitter and he did say that the signal was improved (he said it went from a +2 to a +7 whatever that meant.

He still thinks that, although he fixed some things to bring it up to spec, the issues we're having are equipment related. He said IF it continues to happen, then 99% sure it's the modem.  So I'm going to monitor this for a day or two and see what happens.

And regarding the question about the 16 locked channels vs. 32 channels, he said that some ISP's do 32 channels but RCN is different and they do not. As soon as I started to ask about it, he started shaking his head NO (like he knew I what I was going to ask) so it sounds like an RCN-thing. Bottom line is I'm showing ~900M speed on the download side off my router so I'm getting the bandwidth. Guess I don't care if it's 32 or 16 channels....as long as it stays UP and I fix this possible modem issue. We'll see

[plemans]

Hope it works!

[FURRYe38]

Ok, glad they seem to have got it working better. I guess some ISPs maybe using 16 channels vs 32. If that works for them then I guess it works. Possible there compressing signals into 16 channels. Sounds like it maybe mosty a connection issue since they reported finding bad connections on there side. Also I would chreck the modems FW as well. v1s seem to have more problems. I'm on v2. I believe there is a v3 aswell. 

Hope it keeps working. 

---

@bcooper27 wrote:

RCN Technician came by today.  He initially checked the signal on the cable in my office to check for errors and all looked good...no issues. He checked the connections outside my home and found the connection at the pole and the connections on either side of the underground cable were 'bad.' He also said there was a splitter on the outside of the home that didn't need to be there. She he replaced all the connections and took out the splitter and he did say that the signal was improved (he said it went from a +2 to a +7 whatever that meant.

He still thinks that, although he fixed some things to bring it up to spec, the issues we're having are equipment related. He said IF it continues to happen, then 99% sure it's the modem.  So I'm going to monitor this for a day or two and see what happens.

And regarding the question about the 16 locked channels vs. 32 channels, he said that some ISP's do 32 channels but RCN is different and they do not. As soon as I started to ask about it, he started shaking his head NO (like he knew I what I was going to ask) so it sounds like an RCN-thing. Bottom line is I'm showing ~900M speed on the download side off my router so I'm getting the bandwidth. Guess I don't care if it's 32 or 16 channels....as long as it stays UP and I fix this possible modem issue. We'll see

---

[bcooper27]

So today I took the CM1200 back to Best Buy and told them we've checked everything and the RCN tech even made connection replacements on the cable and sees everything running perfect on their side, but the modem continued to have Internet dropping issues. I told them that after talking with RCN, we figured that if it continued dropping after they made sure everything was fine on the network side, it would HAVE to be equipment issues so I wanted to replace it.

Best Buy swapped it out for another CM1200 and I installed that today about 3:30pm ET.  About 10mins ago (10:10pm or so) the new one did the SAME thing. Internet dropped, the download light was flashing again and I had to reboot to get it back up and running.  SAME problem. Checking the logs it showed same errors as previously shown in posts above.

I can't believe I had two bad modems.  I got them from two different Best Buy stores, not that that makes a difference, but it could. I guess there's a possibility of me getting two bad ones but the odds have to be astronomical.  I fully believe there's a config issue of some sort, quite possibly the firmware. Right now the modem shows Firmware version V2.02.05 which I think is the latest. If I had to bet money, this is the issue. So this begs the question, how do I get the modem on a different version to test it out?  Is this driven by the ISP RCN?

Again, appreciate the help as I continue trying to troubleshoot this problem. I don't want to give up on the Netgear Modem....I've had good luck with all of my Netgear equipment over the years and I want to exhaust every effort before I throw in the towel. 

[plemans]

It is driven by the ISP in terms of firmware. 

Maybe @DarrenM could help out with ISP specifics on modems

[FURRYe38]

Its either a ISP signaling, confifguration issue or the ISP needs to update FW as suggested. Two same model modems experiening same problem would not be a modem problem. 

---

@bcooper27 wrote:

So today I took the CM1200 back to Best Buy and told them we've checked everything and the RCN tech even made connection replacements on the cable and sees everything running perfect on their side, but the modem continued to have Internet dropping issues. I told them that after talking with RCN, we figured that if it continued dropping after they made sure everything was fine on the network side, it would HAVE to be equipment issues so I wanted to replace it.

Best Buy swapped it out for another CM1200 and I installed that today about 3:30pm ET.  About 10mins ago (10:10pm or so) the new one did the SAME thing. Internet dropped, the download light was flashing again and I had to reboot to get it back up and running.  SAME problem. Checking the logs it showed same errors as previously shown in posts above.

I can't believe I had two bad modems.  I got them from two different Best Buy stores, not that that makes a difference, but it could. I guess there's a possibility of me getting two bad ones but the odds have to be astronomical.  I fully believe there's a config issue of some sort, quite possibly the firmware. Right now the modem shows Firmware version V2.02.05 which I think is the latest. If I had to bet money, this is the issue. So this begs the question, how do I get the modem on a different version to test it out?  Is this driven by the ISP RCN?

Again, appreciate the help as I continue trying to troubleshoot this problem. I don't want to give up on the Netgear Modem....I've had good luck with all of my Netgear equipment over the years and I want to exhaust every effort before I throw in the towel. 

---

[tparker20]

this is all very helpful  I too am having the same issues with the downstream light constantly blinking.  We got his modem back in july of 2020 and everything has been fine until now.  I had a tech at the house today and they are trying to say it is the modem.  They connected the ISP modem and were able to get the 900speed but once connecting the CM1200 modem back, all sorts of problems.  Is it truly concluded that the issue is a bad modem, or the ISP no longer wanting to communicate with the CM1200 modem?  Any advice is welcomed as I need to get this back up working with all the zooms required these days from home.

[FURRYe38]

Please post a copy and paste of the modems connection status page.
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...

IF it was actually established that the CM1200 wasn't working well, then you'll need to contact NG support and ask about and RMA. 

---

@tparker20 wrote:

this is all very helpful  I too am having the same issues with the downstream light constantly blinking.  We got his modem back in july of 2020 and everything has been fine until now.  I had a tech at the house today and they are trying to say it is the modem.  They connected the ISP modem and were able to get the 900speed but once connecting the CM1200 modem back, all sorts of problems.  Is it truly concluded that the issue is a bad modem, or the ISP no longer wanting to communicate with the CM1200 modem?  Any advice is welcomed as I need to get this back up working with all the zooms required these days from home.

---

[bcooper27]

The frustration dealing with RCN saying their side ws fine and continued drops on the CM1200 (not one, but TWO CM1200's with the same issue) forced me to try a different modem. I fully believe the issue is firmware/software related between RCN's network and the modem, but I don't have time for them to figure it out.

That being said, the other night I went out and purchased an Arris SB8200 (which I believe is the same modem RCN would install if you lease/rent it from them) and it's worked flawlessly for the past week.

I'm a Netgear guy but my patience on these issues just wore thin. I still have my RAX70 Nighthawk on the other end and that works great, but unfortunately we had to go in a different direction on the modem side. 

Appreciate everyone's help. Sorry it didn't work out with the CM1200.