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Gigabit plan, blue bonded light keeps turning green, caps at 90mbps

Regular Visitor

Gigabit plan, blue bonded light keeps turning green, caps at 90mbps

I'm currently provisioned for gigabit, and used to regularly see 400-600mbps in actual throughput. I have no cable splitters in the house, the incoming line goes straight to the modem. 

For the past week or so, the blue bonded downlink light will turn to green within a few hours of a reboot. My download speeds have degraded to around 90mbps. Upload speeds have been fine at around 30-40mbps.

Resetting the modem will always bring back the blue bonded light, but restoring normal speeds of 400-600mbps speeds is hit or miss, and always degrades back to 90mbps after a few hours.

Does this look like an Xfinity issue? Or should I try purchasing a new modem. I currently have an Arris SB8200 that's around a year old. 

Modem Information:


Standard Specification CompliantDocsis 3.1
Hardware Version6
Software VersionAB01.02.053.01_112320_193.0A.NSH


Here is modem signal data:


Startup Procedure
Acquire Downstream Channel651000000 HzLocked
Connectivity StateOKOperational
Boot StateOKOperational
Configuration FileOK 
DOCSIS Network Access EnabledAllowed 


Downstream Bonded Channels
Channel IDLock StatusModulationFrequencyPowerSNR/MERCorrectedUncorrectables
37LockedQAM256651000000 Hz5.2 dBmV39.4 dB00
13LockedQAM256495000000 Hz5.9 dBmV40.3 dB00
14LockedQAM256507000000 Hz5.9 dBmV40.2 dB00
15LockedQAM256513000000 Hz5.1 dBmV40.1 dB00
16LockedQAM256519000000 Hz5.0 dBmV40.0 dB00
17LockedQAM256525000000 Hz5.2 dBmV39.7 dB00
18LockedQAM256531000000 Hz4.9 dBmV39.7 dB00
19LockedQAM256543000000 Hz4.8 dBmV39.8 dB00
20LockedQAM256549000000 Hz4.9 dBmV39.9 dB00
21LockedQAM256555000000 Hz4.3 dBmV39.6 dB00
22LockedQAM256561000000 Hz4.5 dBmV39.7 dB00
23LockedQAM256567000000 Hz4.2 dBmV38.5 dB00
24LockedQAM256573000000 Hz3.3 dBmV38.9 dB00
25LockedQAM256579000000 Hz3.8 dBmV39.6 dB00
26LockedQAM256585000000 Hz3.1 dBmV39.4 dB00
27LockedQAM256591000000 Hz2.9 dBmV39.2 dB00
28LockedQAM256597000000 Hz4.0 dBmV39.4 dB00
29LockedQAM256603000000 Hz6.2 dBmV39.7 dB00
30LockedQAM256609000000 Hz6.1 dBmV39.8 dB00
31LockedQAM256615000000 Hz3.6 dBmV39.3 dB00
32LockedQAM256621000000 Hz3.1 dBmV39.1 dB00
33LockedQAM256627000000 Hz3.6 dBmV39.2 dB00
34LockedQAM256633000000 Hz4.0 dBmV39.3 dB00
35LockedQAM256639000000 Hz4.6 dBmV39.5 dB00
36LockedQAM256645000000 Hz4.9 dBmV39.4 dB00
38LockedQAM256657000000 Hz5.1 dBmV39.3 dB00
39LockedQAM256663000000 Hz5.3 dBmV39.3 dB00
40LockedQAM256669000000 Hz5.7 dBmV39.5 dB00
41LockedQAM256675000000 Hz5.4 dBmV38.9 dB00
42LockedQAM256681000000 Hz5.9 dBmV39.5 dB00
43LockedQAM256687000000 Hz5.9 dBmV39.4 dB00
44LockedQAM256693000000 Hz5.2 dBmV39.2 dB00
159LockedOther722000000 Hz7.1 dBmV38.5 dB1031609590


Upstream Bonded Channels
ChannelChannel IDLock StatusUS Channel TypeFrequencyWidthPower
11LockedSC-QAM Upstream16400000 Hz6400000 Hz40.0 dBmV
22LockedSC-QAM Upstream22800000 Hz6400000 Hz40.0 dBmV
33LockedSC-QAM Upstream29200000 Hz6400000 Hz40.0 dBmV
44LockedSC-QAM Upstream35600000 Hz6400000 Hz39.0 dBmV
55LockedSC-QAM Upstream40400000 Hz3200000 Hz37.0 dBmV



Here is modem log data:


02/12/2021 05:2224366940615"Dynamic Range Window violation"
02/12/2021 05:22820011005"RNG-RSP CCAP Commanded Power Exceeds Value Corresponding to the Top of the DRW;CM-MAC=<redacted>;CMTS-MAC=<redacted>;CM-QOS=1.1;CM-VER=3.1;"
02/12/2021 05:22730504005"REG-RSP-MP Mismatch Between Calculated Value for P1.6hi Compared to CCAP Provided Value;CM-MAC=<redacted>;CMTS-MAC=<redacted>;CM-QOS=1.1;CM-VER=3.1;"
02/12/2021 05:22680011023"Config File Rejected due to Invalid or Unexpected TLV 11 encoding;CM-MAC=<redacted>;CMTS-MAC=<redacted>;CM-QOS=1.1;CM-VER=3.1;"
02/12/2021 05:22730402003"TLV-11 - Illegal Set operation failed;CM-MAC=<redacted>;CMTS-MAC=<redacted>CM-QOS=1.1;CM-VER=3.1;"
01/01/1970 00:0024366940666"Honoring MDD; IP provisioning mode = IPv6"
01/01/1970 00:00840001003"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=<redacted>;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
02/12/2021 05:2124366940443

"Resetting the cable modem due to docsDevResetNow"


Re: Gigabit plan, blue bonded light keeps turning green, caps at 90mbps

The signal stats are o/k but the error log entries indicate that something is going on. Perhaps there is noise ingress into the line(s) somewhere.


There are other signal stat figures that can't be read by the modem. They are the "Upstream Rx Power" (Upstream Receive Power Level), the "Upstream SNR Ch." (Upstream Signal To Noise Ratio), and the "Upstream ICFR" (In Channel Frequency Response). These are as equally important in diagnosing connectivity issues as are the modem's stats.

I'm going to escalate your issue to the Comcast corporate employees that are available to these boards. They will be able to poll the CMTS to see whether or not everything is in the green zone, see your node / cable plant and modem health, and also see a history plot for the modem. You should get a reply here in your topic. Good luck !

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Official Employee

Re: Gigabit plan, blue bonded light keeps turning green, caps at 90mbps

Hello! I'm truly sorry to hear you've been experiencing service issues with your speeds and I would love to look into this for you further! In order to better assist you please click on my handle "ComcastBillie" and send us a private message with your full name and address.

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Official Employees are from multiple teams within Comcast: CARE, Product, Leadership. We ask that you post publicly so people with similar questions may benefit from the conversation.
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Regular Visitor

Re: Gigabit plan, blue bonded light keeps turning green, caps at 90mbps

Just an update on this thread as it's been a few days. I am really sad, and more or less ready to be resigned to this fate. Has anyone found luck with any sort of escalation process?


A quick update on status:

- So my Arris SB8200 still has the same problem - I lose the bonded light in a few hours, and speed plummets to 90mbps.

- I bought a new modem. A Motorola MB8611. It handles the situation a bit better. After a few hours, the blue solid bonded light starts blinking into a blue negotiating light, but the speed drop isn't as punishing. It looks like the Motorola modem is handling the degradation and noise better.


However, I am truly struggling with the Comcast support agents. Every few hours, I get a single reply with a single question, and the ticket gets kicked down the line to someone else. Sometimes I get the same question, sometimes I get new questions. Sometimes the question is entirely irrelevant. Maybe it's not the representative's intention, but the net feeling that results, is I feel like I'm a hot potato.


Questions' I've gotten that seem relevant and helpful:

- Can you ensure fittings are snug but not too tight? (Got it. You're worried about a COAX loose connection. That's a reasonable troubleshooting ask.)

- Is the modem plugged into wall or surge strip? (Oohh, AC interference. Didn't think of that. Let me try wall and battery (flat and sine wave UPS)



Questions I've gotten that are already answered, or irrelevant, but all delay things by hours:

- Can you reboot the modem? (Yeah, many times)

- Can we reboot the modem? (Go for it. I totally get you need to check it off the list)

- Can we reboot the modem? (Yeah... as many times as you need)

- Can you change ethernet cables? (Can't see how that affects bonding, but, sure)

- Can you check for splitters? (That was in my post, but sure, I'll check again. Nope, no splitters)

- Can you make sure your machine meets specs? (Which machine? It's all downstream of modem. But, sure)

- Can you check to make sure you're not on a VPN? (Wut? Sure, fine.)

- Is your modem and gateway integrated? (Nope.)



For those who've successfully gotten a technician, how do you do it? Is there a list of all of the questions agents ask so I can fill them in advance instead of slowly work through it over the next month?