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intermittent disconnects, several times an hour, T3/T4 timouts & DHCP issues

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Regular Visitor

intermittent disconnects, several times an hour, T3/T4 timouts & DHCP issues

my XFINITY Internet connection is currently getting disconnected several times an hour between 1 and 20 minutes. Often it works fine for hours and then it starts failing. I am not sure if this type of behavior can be triggered by some type of interference from neighbors or weather. Maybe an Xfinity pole/amplifier or even switch/node issues .. who knows. I think I checked pretty much everything I can on my side of the network.
 
The modem status show between 20 and 200 uncorrectables/channel & hour (corrected number is 20-40% of that)
I need to restart the modem several times a day. This recovers service for a while.
The modem also resets automatically due to T3/T4 timeouts
Scanning the system through Xfinity Status center often shows no issues at all. 
The Xfinity outage map shows no outages at my address (zip: 30066), however, it has been showing an exclamation mark in the ZIP code area indicating unplanned outages for 51 .. 500 subscribers ( this value fluctuated from zero to 2,000 throughout the past four weeks).
 
modem: SB6183 (also tested with ASUS CM-16), Signal levels 7-11 dBmV down, 40-45dBmV up
service: 100 Mbps (things were better at lower speed, I upgraded the service just around the time these issues started. Coincidence? That's also the time everyone was stuck at home with the home office.
 
Actions taken:
hours of tech support chat for over four weeks now
restart modem usually works (through Xfinity website and power cycling)
modem reset to factory settings
Xfinity checked outside line; added MoCa filter
replaced modem .. different brand, same issues
added splitter to cool down signals .. issues even worse (more frequent)
running test  software for detailed info about up/downtime (ping three sites, 5 sec increment, show error if the response is > 250ms for more than 20 seconds - typical response time is < 10ms) 
 
Excerpts from ASUS router log info:
 
Jul 13 09:38:41 nat: apply redirect rules
Jul 13 09:38:47 WAN_Connection: ISP's DHCP did not function properly. 
[…]
Jul 13 09:39:48 WAN_Connection: WAN was restored.  
 
Jul 14 14:35:46 WAN_Connection: ISP's DHCP did not function properly.
 
Here are a few entries typically found in the cable modem event log:
No ranging response received T3 timeout.
16 consecutive T3 timeouts while trying to range on upstream channel 3
Started Unicast Maintenance Ranging - No Response received - T3 time-out
Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out
 
 
UPDATE (16JUL2020)
I found a post that described the exact same issue. It was resolved by fixing the line/equipment outside the house (defective booster on the pole) The poster is using the same tools I am using to track outages and posts the same type of status/event logs I can see on my modem. So instead of repeating all this, please refer to https://forums.xfinity.com/t5/Your-Home-Network/Intermittent-dropped-internet/td-p/3254091/page/2 I'll have an Xfinity technician have a look at it tomorrow and I hope they will fix the issue.  

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Regular Contributor

Re: intermittent disconnects, several times an hour, T3/T4 timouts & DHCP issues

Welcome to Comcast, home of Xfinity.  

 

I've been dealing with similar issues for over two years.   It will always be your 3rd party equipment.....never mind that after replacing it you'll continue to have problems.   I suggest one final change.... ISP.... I just ordered Centurylink @ 6Mb download (best I can get) to replace my Xfinity @100Mb; a slow internet is better than no internet.

 

BTW - you should check the SNR levels.   In theory, values at or below 35dB indicate a potential problem though I've been having lots of problems lately with values in the 37-38 dB range.  

 

FWIW,   I see lots of T3 timeouts in my log.... lots of uncorrectable errors.... and lots of outages in the 8-10 minute range.   It really strikes me as odd that my neighbor reports outages around the same times I have them; must be my modem.