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SB8200 stop syncing with DOCSIS3.1 after Xfinity scheduled maintenance

Regular Visitor

SB8200 stop syncing with DOCSIS3.1 after Xfinity scheduled maintenance

I live in Fremont, California and there was a scheduled maintenance according to Xfinity's website last night. The outage was about 30min.

 

After the maintenance, My ARRIS SB8200 stopped syncing with downstream DOCSIS 3.1 channel and the downstream is green now instead of blue before. Also the modem indicating that the DOCSIS 3.1 channel's SNR/MER channel is now 0. My download speed dropped from 850-950Mbps all the way to 350Mbps maximum. Yes, I'm on the Gigabit plan (1000 down 35 up). 

 

I called technical support and rebooted the modem few times without luck. Any suggestions/help would be appreciated. Here is my channel connection page from the modem:

 

Startup Procedure
Procedure Status Comment
Acquire Downstream Channel 651000000 Hz Locked
Connectivity State OK Operational
Boot State OK Operational
Configuration File OK  
Security Enabled BPI+
DOCSIS Network Access Enabled Allowed  

 

 
Downstream Bonded Channels
Channel ID Lock Status Modulation Frequency Power SNR/MER Corrected Uncorrectables
30 Locked QAM256 651000000 Hz 14.0 dBmV 40.3 dB 72 0
1 Locked QAM256 465000000 Hz 13.0 dBmV 41.1 dB 17 0
2 Locked QAM256 471000000 Hz 12.2 dBmV 40.5 dB 30 0
3 Locked QAM256 477000000 Hz 13.1 dBmV 40.9 dB 20 0
4 Locked QAM256 483000000 Hz 13.5 dBmV 41.1 dB 24 0
5 Locked QAM256 489000000 Hz 13.6 dBmV 40.9 dB 30 0
6 Locked QAM256 495000000 Hz 14.1 dBmV 40.8 dB 30 0
7 Locked QAM256 507000000 Hz 13.8 dBmV 40.9 dB 32 0
8 Locked QAM256 513000000 Hz 13.2 dBmV 40.7 dB 41 0
9 Locked QAM256 519000000 Hz 13.4 dBmV 40.9 dB 44 0
10 Locked QAM256 525000000 Hz 12.8 dBmV 40.5 dB 49 0
11 Locked QAM256 531000000 Hz 13.8 dBmV 40.7 dB 38 0
12 Locked QAM256 543000000 Hz 14.3 dBmV 41.1 dB 47 0
13 Locked QAM256 549000000 Hz 14.4 dBmV 41.2 dB 44 0
14 Locked QAM256 555000000 Hz 14.6 dBmV 40.7 dB 61 0
15 Locked QAM256 561000000 Hz 14.3 dBmV 40.9 dB 52 0
16 Locked QAM256 567000000 Hz 14.2 dBmV 40.8 dB 56 0
17 Locked QAM256 573000000 Hz 13.9 dBmV 40.7 dB 54 0
18 Locked QAM256 579000000 Hz 13.8 dBmV 40.8 dB 65 0
19 Locked QAM256 585000000 Hz 13.9 dBmV 40.8 dB 54 0
20 Locked QAM256 591000000 Hz 13.7 dBmV 40.9 dB 65 0
21 Locked QAM256 597000000 Hz 14.0 dBmV 40.9 dB 75 0
22 Locked QAM256 603000000 Hz 14.1 dBmV 40.6 dB 84 0
23 Locked QAM256 609000000 Hz 14.0 dBmV 40.8 dB 78 0
24 Locked QAM256 615000000 Hz 14.4 dBmV 40.6 dB 73 0
25 Locked QAM256 621000000 Hz 14.1 dBmV 40.5 dB 75 0
26 Locked QAM256 627000000 Hz 14.4 dBmV 40.9 dB 70 0
27 Locked QAM256 633000000 Hz 13.9 dBmV 40.9 dB 67 0
28 Locked QAM256 639000000 Hz 14.2 dBmV 40.6 dB 85 0
29 Locked QAM256 645000000 Hz 13.8 dBmV 40.7 dB 90 0
31 Locked QAM256 657000000 Hz 13.6 dBmV 40.4 dB 63 0
48 Locked Other 688000000 Hz 14.9 dBmV 0.0 dB 0 0

 

 
Upstream Bonded Channels
Channel Channel ID Lock Status US Channel Type Frequency Width Power
1 5 Locked SC-QAM 17300000 Hz 6400000 Hz 31.0 dBmV
2 6 Locked SC-QAM 23700000 Hz 6400000 Hz 31.0 dBmV
3 7 Locked SC-QAM 30300000 Hz 6400000 Hz 31.0 dBmV
4 8 Locked SC-QAM 36700000 Hz 6400000 Hz 31.0 dBmV
Expert

Re: SB8200 stop syncing with DOCSIS3.1 after Xfinity scheduled maintenance

The upsrtream power is too high and should be addressed first regardless of anything else. Is there a drop amplifier on the coax line leading to the modem ? If so, remove it as see what happens.



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Regular Visitor

Re: SB8200 stop syncing with DOCSIS3.1 after Xfinity scheduled maintenance

There is no drop amp. However the deployment in our building (recently built) is based on RFoG and there is a RFoG CPE in my closet.

Expert

Re: SB8200 stop syncing with DOCSIS3.1 after Xfinity scheduled maintenance

O/k no wonder it is so strong. Have you tried resetting the 8200 back to factory defaults by depressing and holding in the recessed reset button on the rear for 30 seconds ?



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Regular Visitor

Re: SB8200 stop syncing with DOCSIS3.1 after Xfinity scheduled maintenance

Thanks for your suggestions - I actually found a 8 way splitter in the wiring closet. With the splitter I was able to knock down downstream power by another ~7 dbmv so they are more within the ideal limit.

 

I did a factory reset with the modem after that. Still not connecting at DOCSIS 3.1 speed and the downstream LED is still green. See attached:

 

Startup Procedure
Procedure Status Comment
Acquire Downstream Channel 657000000 Hz Locked
Connectivity State OK Operational
Boot State OK Operational
Configuration File OK  
Security Enabled BPI+
DOCSIS Network Access Enabled Allowed  

 

 
Downstream Bonded Channels
Channel ID Lock Status Modulation Frequency Power SNR/MER Corrected Uncorrectables
31 Locked QAM256 657000000 Hz 7.9 dBmV 40.1 dB 3 0
1 Locked QAM256 465000000 Hz 6.9 dBmV 40.8 dB 0 0
2 Locked QAM256 471000000 Hz 6.7 dBmV 40.7 dB 0 0
3 Locked QAM256 477000000 Hz 7.1 dBmV 40.8 dB 0 0
4 Locked QAM256 483000000 Hz 7.3 dBmV 40.9 dB 0 0
5 Locked QAM256 489000000 Hz 7.4 dBmV 40.8 dB 0 0
6 Locked QAM256 495000000 Hz 7.5 dBmV 40.5 dB 0 0
7 Locked QAM256 507000000 Hz 6.9 dBmV 40.5 dB 0 0
8 Locked QAM256 513000000 Hz 6.7 dBmV 40.4 dB 2 0
9 Locked QAM256 519000000 Hz 6.4 dBmV 40.4 dB 1 0
10 Locked QAM256 525000000 Hz 6.4 dBmV 40.3 dB 0 0
11 Locked QAM256 531000000 Hz 6.9 dBmV 40.2 dB 3 0
12 Locked QAM256 543000000 Hz 7.9 dBmV 40.8 dB 0 0
13 Locked QAM256 549000000 Hz 8.2 dBmV 40.7 dB 0 0
14 Locked QAM256 555000000 Hz 8.5 dBmV 40.8 dB 0 0
15 Locked QAM256 561000000 Hz 8.3 dBmV 40.8 dB 3 0
16 Locked QAM256 567000000 Hz 8.3 dBmV 40.7 dB 2 0
17 Locked QAM256 573000000 Hz 8.0 dBmV 40.7 dB 3 0
18 Locked QAM256 579000000 Hz 7.9 dBmV 40.7 dB 3 0
19 Locked QAM256 585000000 Hz 7.9 dBmV 40.7 dB 1 0
20 Locked QAM256 591000000 Hz 7.8 dBmV 40.6 dB 5 0
21 Locked QAM256 597000000 Hz 7.8 dBmV 40.4 dB 1 0
22 Locked QAM256 603000000 Hz 7.9 dBmV 40.4 dB 0 0
23 Locked QAM256 609000000 Hz 7.9 dBmV 40.5 dB 3 0
24 Locked QAM256 615000000 Hz 7.9 dBmV 40.3 dB 4 0
25 Locked QAM256 621000000 Hz 8.0 dBmV 40.4 dB 2 0
26 Locked QAM256 627000000 Hz 8.1 dBmV 40.4 dB 1 0
27 Locked QAM256 633000000 Hz 7.9 dBmV 40.5 dB 1 0
28 Locked QAM256 639000000 Hz 7.9 dBmV 40.3 dB 3 0
29 Locked QAM256 645000000 Hz 8.0 dBmV 40.3 dB 1 0
30 Locked QAM256 651000000 Hz 8.0 dBmV 40.2 dB 2 0
48 Locked Other 688000000 Hz 8.3 dBmV 0.0 dB 0 0

 

 
Upstream Bonded Channels
Channel Channel ID Lock Status US Channel Type Frequency Width Power
1 7 Locked SC-QAM 30300000 Hz 6400000 Hz 38.8 dBmV
2 5 Locked SC-QAM 17300000 Hz 6400000 Hz 38.3 dBmV
3 6 Locked SC-QAM 23700000 Hz 6400000 Hz 38.5 dBmV
4 8 Locked SC-QAM 36700000 Hz 6400000 Hz 38.3 dBmV
Contributor

Re: SB8200 stop syncing with DOCSIS3.1 after Xfinity scheduled maintenance

As you observed in the first post your modem is not detecting a docsis 3.1 signal ( downstream light is green not blue, ofdm channel 48 has 0 snr) and has fallen back to docsis 3.0 which has a maximum download speed in the neighborhood of 400 mbps.  It is possible that your modem failed during the scheduled maintenance but more likely something Comcast will have to get involved in to correct. Since factory reset did not correct the issue you should contact customer service to have your modem completely removed from your account and reprovisioned. If that fails one of the forum experts can escalate your issue to a Comcast employee,  they can further isolate but may want a tech to visit and check your signals. Good luck. 

Expert

Re: SB8200 stop syncing with DOCSIS3.1 after Xfinity scheduled maintenance

Signals are better but something else is obviously going on. Due to the complexity of your RFoG setup, I'm going to escalate your issue to the Comcast corporate employees that are available to these boards.  You should get a reply here in your topic. Good luck !



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Expert

Re: SB8200 stop syncing with DOCSIS3.1 after Xfinity scheduled maintenance


@jw32097 wrote:

 docsis 3.0 which has a maximum download speed in the neighborhood of 400 mbps.  


That's not necessarily true. The speeds of DOCSIS 3.0 depends on the number of bonded channel being utilized. 

 

A current, single 256 QAM modulated, 6.4 MHz wide, 5.120 MSym/sec downstream cable channel supports a raw data rate of approximately 43 Mbps, and a real world throughput of approximately 38.1 Mbps.

 

Technically, 31 channels can yield 1178 Mbps. 31x38=1178. Smaller cable companies that don't offer DOCSIS 3.1 / an OFDM  channel do it this way.

 

The reason it is 400 with the Comcast system is that when an OFDM channel is not present, the modem falls back to using a lower speed tier configuration / bootfile. It doesn't matter how many 3.0 channels are available in this case because the bootfile governs the top speed.



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Official Employee

Re: SB8200 stop syncing with DOCSIS3.1 after Xfinity scheduled maintenance

Hello @gfwyzxj, thanks for reaching out and I can further assist you with this modem/DOCSIS channel concern! Can you please send me a private message including the full name as it appears on the account and your full name if different? 

 

To send a private message, please click my name "ComcastAmira" then select "Send a Message" on the right side.


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Regular Visitor

Re: SB8200 stop syncing with DOCSIS3.1 after Xfinity scheduled maintenance

Thanks Amira, PM sent

Official Employee

Re: SB8200 stop syncing with DOCSIS3.1 after Xfinity scheduled maintenance

Thanks and I have responded to your private message! 


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Official Employee

Re: SB8200 stop syncing with DOCSIS3.1 after Xfinity scheduled maintenance

@gfwyzxj, I have not heard back from you on here, or in our private message, so I will be locking this thread. Please be sure to send me a private message if you still need assistance with this DOCSIS concern. Please create a new Public post if you need assistance with any other issues or concerns. Thank you! 


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