Visitor
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7 Messages
Internet keeps dropping
I have my own Netgear CM3000 and when it's connected the speed is plenty fast (I have an 800mps plan). However, my internet drops multiple times per day and this has been going on regularly for the past few weeks. We've had service at this address for 12 years (and with this modem for at least a year) and it hasn't been an issue until recently. It only drops for less than 30 seconds, but it's enough to drop my work calls and interrupt tv (I use a non-comcast streaming service). We had a tech out last week who removed an old amp from our line and said our modem was green, but the internet dropped again within 30 minutes of him leaving - and another 5 times that night! At this point our internet is so unreliable I'm researching alternative options, but fiber isn't available in my neighborhood yet.
I looked at my modem log and there seem to be a lot of T3 timeouts, which from these forums seem to suggest there is something wrong further up the line on the Comcast side? This is the log just from today:
Time |
Priority |
Description |
Wed Jun 04 15:38:28 2025 |
(Notice (6)) |
CM-STATUS message sent. Event Type Code: 16; Chan ID: 194; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 3.;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1; |
Wed Jun 04 14:34:35 2025 |
(Critical (3)) |
Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1; |
Wed Jun 04 13:42:46 2025 |
(Critical (3)) |
SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1; |
Wed Jun 04 13:42:44 2025 |
(Critical (3)) |
No Ranging Response received - T3 time-out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1; |
Wed Jun 04 11:26:45 2025 |
(Critical (3)) |
Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1; |
Wed Jun 04 08:29:35 2025 |
(Notice (6)) |
US profile assignment change. US Chan ID: 41; Previous Profile: 13; New Profile: 12 13.;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1; |
Wed Jun 04 08:29:30 2025 |
(Notice (6)) |
DS profile assignment change. DS Chan ID: 33; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1; |
Wed Jun 04 08:29:29 2025 |
(Notice (6)) |
DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1; |
Wed Jun 04 08:29:24 2025 |
(Notice (6)) |
TLV-11 - unrecognized OID;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1; |
Time Not Established |
(Notice (6)) |
Honoring MDD; IP provisioning mode = IPv6 |
Time Not Established |
(Critical (3)) |
SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1; |
Wed Jun 04 08:26:29 2025 |
(Critical (3)) |
Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1; |
Wed Jun 04 03:46:48 2025 |
(Critical (3)) |
Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=xx:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.1; |
Any help is appreciated!
EG
Expert
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111.3K Messages
22 days ago
@user_shp9gc
What do the modem's signal status values look like ?
Please also copy all of the text in its entirety of the *Downstream Power Levels*, the *SNR's* (Signal to Noise Ratios), and the *Upstream Power Level* numbers and paste them into your next post.
Is there a router / WiFi in the mix here ?
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EG
Expert
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111.3K Messages
14 days ago
@user_shp9gc
This may or may not be the root cause of the problem (YMMV) but it should be addressed regardless. First. 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 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, animal chews.
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 !
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