APK17's profile

Frequent Visitor

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13 Messages

Sun, May 9, 2021 12:06 AM

Arris 8200 modem flips between DOCSIS 3.0 and 3.1 (blue light to green)

Howdy, I have an ARRIS 8200 modem and and 1.2 Gbps Xfinity plan.  The downstream light on my Arris 8200 modem changes from blue (DOCSIS 3.1) to Green (DOCSIS 3.0) several times per hour.

I'd been having disconnections from the internet every few days recently and Xfinity sent a tech out today.  They checked everything inside and outside of the house. They did quite a bit of improvement with cable terminations both in and out of the house and even replaced what was apparently the wrong power supply for the Xfinity amplifier in the home's wiring closet. When the tech left he said everything was great now.

It's too early to know if the disconnection issue is resolved - I hope it is, but the issue with the indicator light on the modem flipping back and forth hasn't been resolved and my last speed test using the Xfinity speed test site was sub-500 Mbps on a wired computer.  Not great.

What should I be looking at, signal level wise to figure out if this is a Xfinity issue or a bad modem?

Thank you

Responses

andyross

Silver Problem Solver

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6.9K Messages

2 m ago

Post your signal levels. In particular, the "Other" channel which is the OFDM used for D3.1. You can also try posting your Event Log from the modem.

APK17

Frequent Visitor

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13 Messages

@andyross  Interesting that you should mention the "other" channel.  The Xfinity tech was great (IMO) but he didn't seem to really know what that channel was for when I pointed out that it seems to be having issues.  Here are my signal levels.

 

EG

Expert

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87.2K Messages

2 m ago

Try getting them here; http://192.168.100.1 


Please post the *Downstream Power Level*, the *Upstream Power Level*, and the *SNR* (Signal to Noise Ratio) numbers.

APK17

Frequent Visitor

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13 Messages

@EG  I posted those numbers as requested, thank you for taking a look

EG

Expert

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87.2K Messages

The upstream power is on the high side and it may be intermittently fluctuating even higher to out of spec levels. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels.

In an effort to try to obtain better connectivity / more wiggle room, check to see if there are there any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/re-configured. Any splitters that remain should be high quality and cable rated for 5-1000 MHz, bi-directional, and no gold colored garbage from Radio Shack, Home Depot, Target, etc. Splitters should be swapped with known to be good / new ones to test.

Also check the coax cable for any damage such as cuts, nicks, kinks, sharp bends, etc.

If there aren't any unneeded splitters that can be eliminated and if your coax wiring setup can't be reconfigured so that there is a single two-way splitter connected directly off of the drop from the street / pole with one port feeding the modem and the other port feeding the rest of the house/equipment with additional splits as needed and you've checked all the wiring and fittings for integrity and tightness and refresh them by taking them apart then check for and clean off any corrosion / oxidation on the center wire and put them back together again, then perhaps it's best to book a tech visit to investigate and correct.


Good luck with it !

APK17

Frequent Visitor

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13 Messages

*Knock on wood*  The disconnection issues I had been having seem to be resolved after the tech visit on Saturday.   My remaining issue the DOCSIS 3.1 downstream indicator light falling back to DOCSIS 3.0 ( blue to green light).

The tech and I spoke about the upstream levels.  He indicated to me that anything less than 54 (ideally less than 51) is within spec for the upsteam channels.  While 49 isn't far from 51 I have checked the power levels several times and never seen them any higher. 

There aren't any splitters in the home except for the amplifier that Xfinity installed.  All co-ax cable that is visible is free from kinks or damage.  The tech specifically tested the run that goes to the cable box and said it didn't show signs of anything being amiss with it.

  • Was what the tech told me about power levels incorrect?
  • Perhaps I'm too narrowly thinking of the role the upstream channels play but my upstream speed has always been very good (40/41 Mbps) for what Xfinity provisions.  Could the upstream channels still be affecting downstream speeds?
EG

Expert

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87.2K Messages

1) 54 is too high / out of spec. Comcast disabled the *extended upstream power* feature a while back so 51 is now again the upper limit.

2) Yes. With the way that the TCP IP protocol functions, if there is an upload impairment, the download speeds will suffer as well due to a potential slow down of the TCP ACK (Acknowledgment) packets which travel via the upstream path to get sent back to the sender.

Bear in mind that if the premises facing techs can not find or fix a problem at your home, it is they who are responsible for escalating it to their line / network / maintenance dept. techs. The problem may lie beyond your home in the local neighborhood infrastructure somewhere but it is their S.O.P. to start at the home.


Good luck !

APK17

Frequent Visitor

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13 Messages

@andyross and @EG 

What about the "other" downstream channel as seen in my pictures?   I'm interested to know what role that may play in all of this.

Thank you

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