Consistent DNS Issues

[6910674]

Internet drops throughout the day, both wired and wireless.  Power cycling/resetting modem work, if/when the problem doesn't fix iself on its own (usually 10 minutes).

When it is down, the gateway can still be accessed, and status shows no problems.  I've tried changing the DNS to OpenDNS & GoogleDNS, but problems continue to persist.

Please help.

[BruceW]

Devices often report a "DNS Error" when they are actually having trouble reaching the Internet at all. This is because when you click a link or bookmark the first thing the device needs to do is look up the IP address of the site using DNS. Typically as the page loads this needs to be repeated many times to load all of the page components. If these lookups fail because of a connection problem the device won't be able to access DNS and may incorrectly announce a "DNS Error".

If you want to troubleshoot this yourself, please see Connection Troubleshooting Tips. If you still need help, please post your modem or gateway's signal information, especially downstream power levels and SNR, upstream power levels, and error log. There are usually found at http://10.0.0.1 or http://192.168.100.1.

[6910674]

Downstream bonded channels:

Channel	Lock Status	Modulation	Channel ID	Frequency	Power	SNR	Corrected	Uncorrectables
1	Locked	QAM256	4	417000000 Hz	-1.9 dBmV	43.8 dB	0	0
2	Locked	QAM256	5	423000000 Hz	-2.0 dBmV	43.7 dB	0	0
3	Locked	QAM256	6	429000000 Hz	-2.1 dBmV	43.9 dB	0	0
4	Locked	QAM256	7	435000000 Hz	-2.1 dBmV	43.8 dB	0	0
5	Locked	QAM256	8	441000000 Hz	-2.3 dBmV	43.8 dB	0	0
6	Locked	QAM256	9	447000000 Hz	-2.6 dBmV	43.6 dB	0	0
7	Locked	QAM256	10	453000000 Hz	-2.6 dBmV	43.2 dB	0	0
8	Locked	QAM256	11	459000000 Hz	-2.6 dBmV	43.2 dB	0	0

Upstream channels:

Channel	Lock Status	US Channel Type	Channel ID	Symbol Rate	Frequency	Power
1	Locked	ATDMA	2	5120 Ksym/sec	30100000 Hz	45.8 dBmV
2	Locked	ATDMA	1	5120 Ksym/sec	36500000 Hz	45.5 dBmV
3	Locked	ATDMA	3	5120 Ksym/sec	23700000 Hz	45.5 dBmV
4	Locked	ATDMA	4	5120 Ksym/sec	17300000 Hz	45.8 dBmV

Diagnostic log since 4/19:

Time	Priority	Description
Time Not Established	Notice (6)	Honoring MDD; IP provisioning mode = IPv6
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out
Time Not Established	Notice (6)	WiFi Interface [wl1] set to Channel 149 (Side-Band Channel:N/A) - Reason:INIT
Time Not Established	Notice (6)	WiFi Interface [wl0] set to Channel 1 (Side-Band Channel:N/A) - Reason:INIT
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out
Fri May 29 14:16:41 2020	Critical (3)	Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=74:ea:e8:f8:f4:c3;CMTS-MAC=00:01:5c:65:58:54;CM-QOS=1.1;CM-VER=3.0;
Fri May 29 12:51:11 2020	Critical (3)	Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=74:ea:e8:f8:f4:c3;CMTS-MAC=00:01:5c:65:58:54;CM-QOS=1.1;CM-VER=3.0;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out
Fri May 29 05:56:34 2020	Critical (3)	Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=74:ea:e8:f8:f4:c3;CMTS-MAC=00:01:5c:65:58:54;CM-QOS=1.1;CM-VER=3.0;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out
Tue May 19 22:54:08 2020	Critical (3)	Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=74:ea:e8:f8:f4:c3;CMTS-MAC=00:01:5c:65:58:54;CM-QOS=1.1;CM-VER=3.0;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=74:ea:e8:f8:f4:c3;CMTS-MAC=00:01:5c:65:58:54;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	No Maintenance Broadcasts for Ranging opportunities received - T2 time-out;CM-MAC=74:ea:e8:f8:f4:c3;CMTS-MAC=00:01:5c:65:58:54;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out
Time Not Established	Critical (3)	No Maintenance Broadcasts for Ranging opportunities received - T2 time-out;CM-MAC=74:ea:e8:f8:f4:c3;CMTS-MAC=00:01:5c:65:58:54;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out
Time Not Established	Critical (3)	No Maintenance Broadcasts for Ranging opportunities received - T2 time-out;CM-MAC=74:ea:e8:f8:f4:c3;CMTS-MAC=00:01:5c:65:58:54;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out
Time Not Established	Critical (3)	No Maintenance Broadcasts for Ranging opportunities received - T2 time-out;CM-MAC=74:ea:e8:f8:f4:c3;CMTS-MAC=00:01:5c:65:58:54;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=74:ea:e8:f8:f4:c3;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=74:ea:e8:f8:f4:c3;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Sun Apr 19 23:52:10 2020	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=74:ea:e8:f8:f4:c3;CMTS-MAC=00:01:5c:65:58:54;CM-QOS=1.1;CM-VER=3.0;
Sun Apr 19 23:52:10 2020	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=74:ea:e8:f8:f4:c3;CMTS-MAC=00:01:5c:65:58:54;CM-QOS=1.1;CM-VER=3.0;
Sun Apr 19 23:51:41 2020	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=74:ea:e8:f8:f4:c3;CMTS-MAC=00:01:5c:65:58:54;CM-QOS=1.1;CM-VER=3.0;
Sun Apr 19 23:51:41 2020	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=74:ea:e8:f8:f4:c3;CMTS-MAC=00:01:5c:65:58:54;CM-QOS=1.1;CM-VER=3.0;
Sun Apr 19 23:51:07 2020	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=74:ea:e8:f8:f4:c3;CMTS-MAC=00:01:5c:65:58:54;CM-QOS=1.1;CM-VER=3.0;
Sun Apr 19 23:51:07 2020	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=74:ea:e8:f8:f4:c3;CMTS-MAC=00:01:5c:65:58:54;CM-QOS=1.1;CM-VER=3.0;
Sun Apr 19 23:50:48 2020	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=74:ea:e8:f8:f4:c3;CMTS-MAC=00:01:5c:65:58:54;CM-QOS=1.1;CM-VER=3.0;
Sun Apr 19 23:50:47 2020	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=74:ea:e8:f8:f4:c3;CMTS-MAC=00:01:5c:65:58:54;CM-QOS=1.1;CM-VER=3.0;
Sun Apr 19 23:48:22 2020	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=74:ea:e8:f8:f4:c3;CMTS-MAC=00:01:5c:65:58:54;CM-QOS=1.1;CM-VER=3.0;

[BruceW]

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@6910674 wrote: Downstream bonded channels: ... Upstream channels: ... Diagnostic log ...

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The signals you posted look OK. The error log is difficult to interpret since the entries for date and time were not included. Suggest you continue to monitor the signal levels to see if they are "wandering" into out-of-spec territory.

If you can't find the problem call Comcast at the phone number on your bill or 1-800-Comcast, or use one of the options on https://www.xfinity.com/support/contact-us/. If they can't fix the problem remotely (unlikely), insist they send a tech out to identify the cause and correct it.

If the tech finds bad coax, splitters, amplifiers, or connections in your home (even if Comcast originally supplied them) you'll probably have to pay for the visit unless you have their Service Protection Plan (https://www.xfinity.com/support/articles/service-protection-plan, closed to customers that don't already have it). If the trouble is due to a faulty Comcast rental device, or anything outside your home, you shouldn't be charged.