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Gigabit connectivity issues

Frequent Visitor

Gigabit connectivity issues

I've had on and off issues with my gigabit internet service that started a couple of months ago.  Initially had a MB8600 modem that worked great for 3-4 months without a hitch.  Then I started getting intermittent disconnects despite modem having full connection and router still able to get an IP address.  Specifically the connection appeared to "lag" out, with some instances of a speed test getting a ping,  but only 0-1 mbps of speed.  Sometimes a speed test a minute or two later would have full speeds when re-testing.  Event logs on the MB8600 showed issues with synchronization and T3/T4 time outs. 

 

I had a tech visit in January and was told that the lines to the apartment complex were fine, and 2 other gigabit users had no issues (not sure if they had Xfinity modems though).  Interestingly when I use my older SB6141 I didn''t get any issues with disconnects.  So I went out and bought a CM1100 thinking this perhaps was a modem issue.  However I'm still getting the same problems in terms of intermittent disconnects.  Based on two separate modems from different brands I don't think it would be an issue with the modems.  And with my SB6141 working still maybe this is an issue with DOCSIS 3.1

 

I've seen a good amount of posts about issues with MB8600 and connection issues so I'm hoping someone here will be able to help me, as I'm getting tired of switching back and forth between modems when I get an unstable connection.

Expert

Re: Gigabit connectivity issues

What do the modem's signal stats look like ? 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.




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Frequent Visitor

Re: Gigabit connectivity issues

Please see the attached images.  Power levels are taken when the internet with the CM1100 is working fine.  Some of the time not established events may have been when I disconnected the cable to switch to the other modem but left the CM1100 power on.  I'll screenshot power levels the next time the disconnects happen.

2-6-19 cm1100 partial event log.jpg2-6-19 cm1100 power levels A.jpgPower levels 12-6-19 cm1100 power levels B.jpgPower levels 2

Frequent Visitor

Re: Gigabit connectivity issues

Here's when I just suffered another disconnect, followed by more intermittent disconnects (other examples not shown aside from when I first initially noticed it).  Broadband test often able to get a ping, but no download speed whatsoever.  Other times it can't get a ping.2-6-19 cm1100 disconnect log.jpg2-6-19 cm1100 disconnected power levels B.jpg2-6-19 cm1100 disconnected power levels A.jpg

 

 

Expert

Re: Gigabit connectivity issues

Can't see your pics. Since you are a new poster, they likely need to be approved by a Forum Admin. Or you may need to make a minimum number of posts.

You could try hosting them at one of those free third-party pic hosting sites and post the link to them here.



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Frequent Visitor

Re: Gigabit connectivity issues

I think an admin allowed some of the pictures now.

Expert

Re: Gigabit connectivity issues

The upstream power is a bit on the high side (especially on channel number 4) and may be intermittently fluctuating even higher out of spec. That can cause random disconnects, spontaneous re-booting of the modem, and speed and latency problems.

In a self troubleshooting 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 5-1002 MHz, bi-directional, and no gold colored garbage types like GE, RadioShack, RCA, Philips, Leviton, Magnavox, and Rocketfish from big box stores like Home Depot, Lowes, Target, Wal-Mart etc. Splitters should be swapped with known to be good / new ones to test

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.




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Frequent Visitor

Re: Gigabit connectivity issues

Thanks for your reply, the modem is connected straight off the wall.  I also tried the other coax outlet that I have Xfinity DVR hooked up to and it didn't make a difference.  I already had a tech team come out in January and they couldn't find any issues with the line outside or inside the apartment with their equipment.  The power levels were fine that day (unfortunately).  So I'm not sure if another tech visit would help, and the first visit already cost $70.

Contributor

Re: Gigabit connectivity issues

Call them and they will remove that $70 fee as it's not your fault and they need to correct this. You don't pay for a truck roll unless there is nothing wrong and it was a frivolous call. In your case there IS something wrong that needs to be addressed. I'm having similar issues but my post dissappeared without any notice. I have a Arris SB8200 and I get timeouts every half hour and it forces my modem to reset. I do get my speeds of Gigabit but it comes and goes and my signal levels are also very good. I did as you did and tried to get someone on these forums to help me with my issue but they simply deleted my post and never said anything.
Expert

Re: Gigabit connectivity issues


@FifthE1ement wrote:
Call them and they will remove that $70 fee as it's not your fault and they need to correct this. .

There is a fee if the problem is found to be on the customer's side of the demarcation point (typically that's the grounding block). If it's on the Comcast system side there should be no charge.



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