Intermittent disconnects and packet loss

Please post a trace to a host that has the troublesome IP along the route.

(Your post will be visible once Comcast approves the image it contains. See https://forums.xfinity.com/conversations/getting-started/disappearing-forum-posts/606894c37437b81d05b7b638?commentId=606b25cb322c887da0f3c0a2.)

The image resolution is so low that I can't see it very well, but as best I can tell the trace continues past the hop you highlighted and reaches the destination with little packet loss, so the apparent loss at the intermediate hops is probably not significant. Please see https://www.dslreports.com/faq/14068.

Are you connecting via Wifi or Ethernet? If Wifi, it's best to switch to an Ethernet cable connection if possible for testing.

If you want to troubleshoot this yourself, please see Internet Troubleshooting Tips. If you still need help, please post your Internet plan speed and the following information from your modem or gateway:

• model number
• downstream power levels and SNR
• upstream power levels
• event log, if available (Be sure to remove or blot out any MAC addresses. Forum security processing considers them "personal information" and may prevent the event log from posting if these are present.)

I am using a NetGear CM600 modem (serial number 4DF597WEA04DD). I am connected via ethernet with a 100 Mbps plan. I have also tested it with a different modem / router combo to no avail. 

Downstream power levels:

Channel	Lock Status	Modulation	Channel ID	Frequency	Power	SNR	Correctables	Uncorrectables
1	Locked	QAM256	17	519000000 Hz	8.6 dBmV	40.5 dB	0	0
2	Locked	QAM256	1	393000000 Hz	6.6 dBmV	39.9 dB	0	0
3	Locked	QAM256	2	399000000 Hz	6.8 dBmV	39.9 dB	0	0
4	Locked	QAM256	3	405000000 Hz	6.9 dBmV	40.0 dB	0	0
5	Locked	QAM256	4	411000000 Hz	6.6 dBmV	39.8 dB	0	0
6	Locked	QAM256	5	429000000 Hz	7.2 dBmV	40.1 dB	0	0
7	Locked	QAM256	6	435000000 Hz	7.1 dBmV	40.1 dB	0	0
8	Locked	QAM256	7	441000000 Hz	7.3 dBmV	40.1 dB	0	0
9	Locked	QAM256	8	447000000 Hz	7.2 dBmV	40.0 dB	0	0
10	Locked	QAM256	9	453000000 Hz	7.3 dBmV	40.1 dB	0	0
11	Locked	QAM256	10	459000000 Hz	7.2 dBmV	40.1 dB	0	0
12	Locked	QAM256	11	465000000 Hz	7.4 dBmV	40.1 dB	0	0
13	Locked	QAM256	12	471000000 Hz	7.6 dBmV	40.2 dB	0	0
14	Locked	QAM256	13	477000000 Hz	7.6 dBmV	40.2 dB	0	0
15	Locked	QAM256	14	483000000 Hz	8.0 dBmV	40.3 dB	0	0
16	Locked	QAM256	15	489000000 Hz	7.9 dBmV	40.2 dB	0	0
17	Locked	QAM256	16	495000000 Hz	7.9 dBmV	40.9 dB	0	0
18	Locked	QAM256	18	525000000 Hz	8.4 dBmV	40.9 dB	0	0
19	Locked	QAM256	19	531000000 Hz	8.6 dBmV	41.3 dB	0	0
20	Locked	QAM256	20	537000000 Hz	8.8 dBmV	41.4 dB	0	0
21	Locked	QAM256	21	543000000 Hz	8.9 dBmV	41.3 dB	0	0
22	Locked	QAM256	22	549000000 Hz	8.8 dBmV	41.4 dB	0	0
23	Locked	QAM256	23	555000000 Hz	8.6 dBmV	41.2 dB	0	0
24	Locked	QAM256	24	561000000 Hz	9.0 dBmV	41.4 dB	0	0

Upstream power levels:

Channel	Lock Status	US Channel Type	Channel ID	Symbol Rate	Frequency	Power
1	Locked	ATDMA	93	5120 Ksym/sec	36500000 Hz	41.0 dBmV
2	Locked	ATDMA	95	5120 Ksym/sec	23700000 Hz	40.0 dBmV
3	Locked	ATDMA	96	5120 Ksym/sec	17300000 Hz	39.5 dBmV
4	Locked	ATDMA	94	5120 Ksym/sec	30100000 Hz	40.3 dBmV
5	Not Locked	Unknown	0	0 Ksym/sec	0 Hz	0.0 dBmV
6	Not Locked	Unknown	0	0 Ksym/sec	0 Hz	0.0 dBmV
7	Not Locked	Unknown	0	0 Ksym/sec	0 Hz	0.0 dBmV
8	Not Locked	Unknown	0	0 Ksym/sec	0 Hz	0.0 dBmV

Event log with Mac Addresses censored:

2021-10-02, 09:01:28	Notice (6)	Honoring MDD; IP provisioning mode = IPv6
2021-10-02, 09:01:12	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-10-02, 09:00:00	Warning (5)	MDD message timeout;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-10-02, 08:59:57	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-10-02, 08:59:56	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-10-02, 08:59:51	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-10-02, 08:59:50	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-10-02, 08:57:26	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-10-02, 08:57:26	Warning (5)	MDD message timeout;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-10-02, 08:57:19	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-10-02, 08:57:19	Warning (5)	MDD message timeout;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-09-30, 09:21:01	Critical (3)	Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-09-30, 08:20:06	Critical (3)	Resetting the cable modem due to docsDevResetNow
2021-09-28, 12:57:05	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-09-28, 12:57:04	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-09-28, 12:56:42	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-09-28, 12:56:33	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-09-28, 12:56:16	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-09-28, 12:50:52	Critical (3)	Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-09-28, 11:42:20	Critical (3)	Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-09-28, 11:18:08	Critical (3)	Resetting the cable modem due to docsDevResetNow
2021-09-27, 15:59:10	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-09-27, 15:59:07	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-09-27, 15:59:03	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-09-27, 15:58:46	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-09-27, 15:58:01	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.0;CM-VER=3.0;
2021-09-27, 15:57:55	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.0;CM-VER=3.0;
2021-09-27, 15:57:48	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-09-27, 15:56:01	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=XXX;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
2021-09-27, 15:54:01	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=XXX;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
2021-09-27, 15:53:58	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-09-27, 15:53:58	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-09-27, 15:53:20	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-09-27, 15:53:19	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
2021-09-27, 15:53:02	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.1;CM-VER=3.0;
Time Not Established	Critical (3)	Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Notice (6)	Honoring MDD; IP provisioning mode = IPv6
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=XXX;CMTS-MAC=XXXXX;CM-QOS=1.0;CM-VER=3.0;

Here is an example of packet loss starting from a comcast node going to google: https://imgur.com/a/tVoSxq3

Thank you for the updated image, but my interpretation is the same: the apparent packet loss and latency is most likely due to the routers at intermediate hops assigning low priority to responses to trace packets. If they were were actually dropping packets or delaying them you would see that in all the subsequent hops.

If you could supply the information requested above we might have a better idea what's going on.

Your latest PingPlotter image appears to show 96.7% packet loss beginning at the 3rd Comcast hop and continuing on into Google's 1e100 network. The downstream power level to your modem is a little high, but I doubt if it's high enough to be causing this.

The error log has a number of entries that suggest it is having trouble communicating with Comcast's network. Although the stats posted look OK, there are other signal stats that the modem doesn't report. So we don't really know if there is a problem at Comcast, or if there is an intermittent connection between their network and your modem.

I'd suggest having the premise techs back out for another look. If you don't want to do that, the "contact me" link on https://www.xfinity.com/hub/customer-experience/xfinity-customer-care-update might be worth a try. Be aware that replies from that office vary from extremely helpful to nonsensical.

I am having something similar happen as well. It's like the internet is constantly blinking, the signal goes from strong to choppy within seconds constantly. It only started in the last 2 weeks. Sometimes my devices can't find the internet at all. Speed test show either great bandwidth or it can't complete the test. I have a modem + route from Xfinity and haven't done any of my own tests yet.

@audly_speedy 

Please create a new topic of your own here on this board detailing your issue and I will attempt to assist you there. Please do not hijack someone else's help thread in progress. Multiple posters piling on to and being helped in a single thread becomes too complicated. confusing, and convoluted. And it's unfair to the original poster. Thank you. 

Are the modem errors suggesting that there is a problem with the modem itself, or just with its connection to the network? The modem is less than 2 weeks old and one that is recommended by Comcast, so I'd hope that it is functional.

I'm not willing to have another tech out here again at this point. I've been burned by them showing up for 5 minutes, saying everything looks good, and charging me 100 bucks, so I'd like to do what I can myself. In any case, I have yet another set of coax cables coming that I'll try out, as well as a 3rd modem. I'll try the "contact me" page and see where that gets me. I'm not really sure what else to try beyond that except for a different internet plan that might route my traffic differently.

Although it's possible for the errors a modem reports to indicate a problem with the modem, they are much more likely to be caused by weak or noisy network signals or a poor connection to the network.

UPDATE: I replaced my modem with one that Comcast sent, tried switching to a 400 Mbps plan, and replaced coax cable again. If anything the problem is worse. Are frequent disconnects just to be expected with Comcast service? Interestingly the one thing that I tried that did work was using a mobile hotspot to connect to the internet. I feel like I am out of options in trying to work with Comcast to resolve this issue.

It seems that I am not getting a good connection with the Comcast servers(?). This occurs 1-2 times per hour. https://imgur.com/hPsuJWT

@user_23a836 wrote: "... This occurs 1-2 times per hour. ..."

The only advice I can offer is keep leaning on them until they fix this.

Is there a way to get a Comcast rep's eyes on this issue? Explaining the problem half a dozen times over chat / phone only for them to reset my modem is quite discouraging. If I could direct them to this thread they might have a better idea of what's going on.

@user_23a836  I'm going to escalate your issue to the Comcast corporate employees that are available to these boards. You should get a reply here in your topic. Good luck !