12 Messages
Highly variable internet speed - logs show uncorrectable code words on Downstream OFDM Channel 1
For months now, we've been seeing intermittent internet and highly variable speeds - multiple technicians have been out and unable to solve the issue. To be sure it wasn't too many devices on the XB8 Xfinity gateway, I purchased a NightHawk CM2050V modem along with a NightHawk BE12000 (RS500) WiFi7 router. The problem has persisted.
After figuring out how to view the cable connection statistics through the modem, I'm seeing that most of the channels look good, but one stands out as possibly the problem:
Downstream OFDM Channels
Channel LockedStatus ProfileID ChannelID Frequency Power SNR/MER ActiveSubcarrier Unerror Correctable Uncorrectable
1 Locked 0 ,1 ,2 ,3 48 850000000 Hz -5.32 dBmV 37.6 dB 1108 ~ 2987 7929666275 7459832055 1567819
2 Not Locked 0 0 0 Hz 0 dBmV 0 dB 0 ~ 4095 0 0 0
This along with a pretty consistent "notice (6)" and "critical (3)" error messages in the modem log:
Tue Apr 15 19:15:25 2025 Notice (6) CM-STATUS message sent. Event Type Code: 16; Chan ID: 48;
Mon Apr 14 16:33:37 2025 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
These appear to coincide with the points at which my internet runs either incredibly slowly or loses connection entirely.
While it's possible there could be a problem (damage) in my cable line running through the roof, I see the same issues when I plug directly into the line on the first floor that shows no sign of damage or kinking.
I have the incoming cable line, with a single splitter (1 to 3, 1 is open and unterminated) - one line goes to the cable on the first floor, the second line runs under the roof to the second floor bedroom where the modem resides.
Any ideas how to get this fixed? Do the readings show there's a problem?
Thanks
user_te
User_te
12 Messages
11 days ago
I'm new to posting new topics on the board, do new topic posts always start listed as "private" in the upper right?
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Aceq2jot
Contributor
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112 Messages
10 days ago
I think you will find this is all part of the back-end upgrades. The OFDM channel is one that I believe from what I have read will change over to OFDMA when they enable X-Class in your area. Honestly the correctable codewords are fine it is more a very high number of uncorrectable you need to look for on the primary channel. My primary channel is 20 and when I have had high uncorrectable code words, I unplug my gateway for a few minutes to reboot and apply any software changes that may have been pushed.
Sadly, due to Xfinity doing a lot of network upgrades to get us to 2gig and above through fiber over coax and occasionally part of the process is slower speeds which are teething problems and clear up on their own. Yes, a slowdown is a bummer but in the long run it will be worth it, and it seems for you like it is for me it is only occasional. For the most part i have found the slow speeds fix themselves after a reboot.
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XfinityVianney
Official Employee
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2.1K Messages
10 days ago
Hi @User_te,
Thank you for reaching out. I hope you are doing well today. I see you've had techs out already, but you haven't seen any changes on your end yet. I'm sorry to hear about that, however, I'll be glad to help. I would like to review the notes from the previous visits, so we can determine the next best steps. When you have a moment, please send me a direct message with your full name and address to get started.
To send a direct message, please click on the chat icon in the top-right corner of the screen, and select "Xfinity Support" to initiate a Direct Message.
Click "Sign In" if necessary
Click the "direct messaging" icon or https://forums.xfinity.com/direct-messaging
Click the "New message" (pencil and paper) icon
Type "Xfinity Support" in the "To:" line and select "Xfinity Support" from the drop-down list which appears. The "Xfinity Support" graphic replaces the "To:" line
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Press Enter to send it
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