Internet keeps going out- Modem reboot resolves

The upstream power is too high 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 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 from Home Depot, Target, Wal-Mart, 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, abrasions, 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 !

My replies above aren't showing as posts.

99.9 % it's the line, not the modem ! If you don't need the splitter you should remove it completely. You could bypass it for a test and see.

Xfinity tech came by on Aug 1st. Spent a few minutes outside only, called me when he was out there and said everything looks fine and that there’s a problem in my neighborhood and nothing has been done about it because not a lot of people in my neighborhood have Xfinity (no way that’s true as I live in a crowded suburban neighborhood in NJ and almost everyone has Xfinity or Fios). He said he’d put a ticket in for it and go up on my pole to check there before he left. I watched him leave almost immediately from my window.

Called today and they had another tech come. He seemed surprised that a tech was at my house recently because he found water in my line almost immediately. He just got finished replacing lots of coax a few minutes ago. We’ll see how it goes.

ETA: My tenant upstairs just got home and told me her Fios is out. The tech obviously did something to affect her Fios connection. 🙄

Hope that does it ! Please update your topic again in a few days. Good luck !

Apparently changing coaxial cable from the outside of my house to the inside didn't fix the issue. 

In the title of this thread I wrote that a modem re-boot resolves the issue. I think that may have been a coincidence. Internet goes out and comes back after about 5 minutes on its own. Here are my logs as of a few minutes ago:

Log

Time   Priority   Description   Time Not Established   Critical (3)   No Ranging Response received - T3 time-out;CM-MAC=00:**:**:**:a*:**;CMTS-MAC=00:**:*c:**:e*:**;CM-QOS=1.0;CM-VER=3.0;   Time Not Established   Notice (6)   Honoring MDD; IP provisioning mode = IPv6   Mon Aug 05 17:23:33 2024    Critical (3)   Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=00:**:**:**:a*:**;CMTS-MAC=00:01:*c:*:e*:**;CM-QOS=1.1;CM-VER=3.0;   Mon Aug 05 17:23:33 2024    Critical (3)   Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=00:**:**:**:a*:**;CMTS-MAC=00:0*:*c:**:e*:**;CM-QOS=1.1;CM-VER=3.0;   Mon Aug 05 17:23:33 2024    Critical (3)   16 consecutive T3 timeouts while trying to range on upstream channel 2;CM-MAC=00:**:**:**:a*:**;CMTS-MAC=00:**:*c:**:e*:**;CM-QOS=1.1;CM-VER=3.0;   Mon Aug 05 17:24:08 2024    Critical (3)   Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=00:**:**:**:a*:**;CMTS-MAC=00:**:*c:**:e*:**;CM-QOS=1.1;CM-VER=3.0;   Mon Aug 05 17:24:08 2024    Critical (3)   Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=00:**:**:**:a*:**;CMTS-MAC=00:**:*c:**:e*:**;CM-QOS=1.1;CM-VER=3.0;   Mon Aug 05 17:24:08 2024    Critical (3)   16 consecutive T3 timeouts while trying to range on upstream channel 1;CM-MAC=00:**:**:**:a*:**;CMTS-MAC=00:**:*c:**:e*:**;CM-QOS=1.1;CM-VER=3.0;   Mon Aug 05 17:24:14 2024    Critical (3)   Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=00:**:**:**:a*:**;CMTS-MAC=00:**:*c:**:e*:**;CM-QOS=1.1;CM-VER=3.0;   Mon Aug 05 17:28:34 2024    Critical (3)   Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=00:**:**:**:a*:**;CMTS-MAC=00:**:*c:**:e*:**;CM-QOS=1.1;CM-VER=3.0;   Mon Aug 05 17:30:47 2024    Critical (3)   No Ranging Response received - T3 time-out;CM-MAC=00:**:**:**:a*:**;CMTS-MAC=00:**:*c:**:e*:**;CM-QOS=1.0;CM-VER=3.0;   Mon Aug 05 17:31:06 2024    Notice (6)   Honoring MDD; IP provisioning mode = IPv6   Wed Aug 07 08:46:15 2024    Critical (3)   Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=00:**:**:*a0:**;CMTS-MAC=00:**:*c:**:e*:**;CM-QOS=1.1;CM-VER=3.0;   Wed Aug 07 08:46:15 2024    Critical (3)   Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=00:**:**:**:a*:**;CMTS-MAC=00:**:*c:**:e*:**;CM-QOS=1.1;CM-VER=3.0;   Wed Aug 07 08:46:15 2024    Critical (3)   16 consecutive T3 timeouts while trying to range on upstream channel 3;CM-MAC=00:**:**:**:a0:**;CMTS-MAC=00:0*:*c:**:e*:**;CM-QOS=1.1;CM-VER=3.0;   Wed Aug 07 08:46:34 2024    Critical (3)   Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=00:**:**:**:a0:**;CMTS-MAC=00:01:*c:**:e*:**;CM-QOS=1.1;CM-VER=3.0;   Wed Aug 07 08:50:54 2024    Critical (3)   Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=00:**:**:**:a0:**;CMTS-MAC=00:0*:*c:**:e*:**;CM-QOS=1.1;CM-VER=3.0;   Wed Aug 07 08:51:15 2024    Critical (3)   No Ranging Response received - T3 time-out;CM-MAC=00:**:**:**a0:**;CMTS-MAC=00:**:*c:**:e*:**;CM-QOS=1.0;CM-VER=3.0;   Wed Aug 07 08:51:58 2024    Notice (6)   Honoring MDD; IP provisioning mode = IPv6

Startup Sequence

Startup Step Status Comment       Acquire Downstream Channel 429000000 Hz Locked       Upstream Connection OK Operational       Boot State OK Operational       Configuration File OK       Security Enabled BPI+

Connection Status

System Up Time 1 days 17h:52m:23s         Network Access Allowed

Downstream Bonded Channels

Channel Lock Status Modulation Channel ID Freq. (MHz) Pwr (dBmV) SNR (dB) Corrected Uncorrected 1 Locked QAM256 1 429.0 3.3 42.8 3555 1269 2 Locked QAM256 42 405.0 3.2 42.6 3870 1142 3 Locked QAM256 43 411.0 3.2 42.8 4212 988 4 Locked QAM256 44 417.0 3.2 42.8 3675 1240 5 Locked QAM256 45 423.0 3.2 42.8 3671 1025 6 Locked QAM256 2 435.0 3.2 42.7 3188 999 7 Locked QAM256 3 453.0 2.9 42.4 2659 946 8 Locked QAM256 4 459.0 2.8 42.2 2957 883 9 Locked QAM256 5 465.0 2.8 42.2 2644 960 10 Locked QAM256 6 471.0 2.7 42.0 2649 924 11 Locked QAM256 7 477.0 2.8 42.3 2713 1056 12 Locked QAM256 8 483.0 2.9 42.4 2724 967 13 Locked QAM256 9 489.0 3.0 42.4 2491 754 14 Locked QAM256 10 507.0 3.3 37.7 2027 695 15 Locked QAM256 11 513.0 3.2 42.6 1898 937 16 Locked QAM256 12 519.0 3.4 42.8 1924 799 17 Locked QAM256 13 525.0 3.4 43.6 1866 1522 18 Locked QAM256 14 531.0 3.3 44.0 1801 1553 19 Locked QAM256 15 537.0 3.3 43.5 1812 1434 20 Locked QAM256 16 543.0 3.2 43.8 1774 1473 21 Locked QAM256 17 549.0 3.1 43.9 1701 1536 22 Locked QAM256 18 555.0 3.1 44.0 1686 1426 23 Locked QAM256 19 561.0 2.2 43.5 1755 1433 24 Locked QAM256 20 567.0 2.7 43.6 1611 1348 Total             60863 27309

Upstream Bonded Channels

Channel Lock Status Channel Type Channel ID Symb. Rate (Ksym/sec) Freq. (MHz) Pwr (dBmV) 1 Locked ATDMA 17 5120 16.3 47.5 2 Locked ATDMA 18 5120 22.8 47.0 3 Locked ATDMA 19 5120 29.2 48.0 4 Locked ATDMA 20 5120 35.6 48.5 5 Not Locked Unknown 0 0 0 0.0 6 Not Locked Unknown 0 0 0 0.0 7 Not Locked Unknown 0 0 0 0.0 8 Not Locked Unknown 0 0 0 0.0

You need to keep getting the techs re-involved until things get fixed properly. 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 up 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. And if the problem is found to be on their side of the demarcation point, there will not be any charge.

Good luck !

Supervisor cam to the house today. Replaced the cable from the pole to the house. I asked him if he saw anything obviously wrong and he didn't. Said the cable had a date of 2019 on it and no obvious bad signs. Gave me his work number and told me to text him if problem persists. We'll see how the next few days goes.

I just noticed the Xfinity employee post from BryanH. If problem persists, I'll text the supervisor that was here today and also contact BryanH. Thanks.