Nighthawk c7800 cable modem

[Monte70car]

Is it a known issue for a cable modem to go out and come back online within a day or two going out? We have had our nighthawk for a year now no issue until October 2020 when we lost internet for a holiday weekend. Comcast/xfinity came out they had a field tech doing a repair a few neighbor hoods over. Once the repair was done internet came up and worked until mid November where it went off again for a day and came back up the following day(local outage). Dec 30th comes we had been working from home everything was good. Get off the computers and go watch a movie and internet goes out at 6pm and doesn’t come back until January 3. Everything is going smooth January 15th rolls around and no internet. I have looks and saw people had the similar issue with the same ISP company and saw some of the question that was ask of them to try. I already changed the wireless channels from auto to a hard number (9 no one on that channel as of last night) 5ghz was left on 153 again no one but our system on it. The downstream power is all over the place 7 to 10 and the upstream power is 32.5-33. I asked if they can change the power numbers and was told no they don’t have the ability to change those numbers. I asked about the firmware if it needed to be updated was told we don’t push firmware to personal routers you have to update if it’s not correct. Am I over thinking that my router can’t be bad if I had internet access days before it goes out my modem ain’t the problem? From what the router is telling my the firmware is 3.01.43.

[plemans]

do you have a screen snip of the cable connections page and the logs? 

those help us more than just telling us what some of the values are. 

they don't "change" the power levels. to change them they'd actually have to come out and check lines which is why a call rarely helps the first time. 

[Monte70car]

I do have pictures but they won’t load as the format doesn’t match what’s allowed. And the computer isn’t getting out of the internal network. Plemans the sad part is a tech or so called tech was here. Took his little tool connected to the feed line going up to the modem and saw that the modem was offline and he did a reboot via his cell phone.

[plemans]

Not giving you grief but if the modem's offline, he couldn't have remote rebooted/reset it. Since it isn't online. 

If you take a screensnip, it should be in the proper format and you can click on "choose file" to add. 

[Monte70car]

Plemans here is what I am able to grab from modem. I’m not 100% but shouldn’t downstream and upstream kinda match? Also the log is here as well second set of line items. As for screen shoots my iPhone comes up as jpeg.
Downstream OFDM Channels
Channel Channel ID Indicator Subcarrier Zero Frequency Active Subcarrier Number Range Total Codewords Uncorrectable Codewords
1 25 Non-Primary 713600000 Hz 1108 ~ 2987 2431991 0
2 0 Other 0 Hz 0 ~ 0 0 0
Upstream OFDMA Channels
Channel UpstreamIsMuted Ranging Status Subcarrier Zero Frequency Active Subcarrier Number Range Symbols Per Frame Tx Power
1 Other 0 Hz 0 ~ 0 0 0 dBmV
2 Other 0 Hz 0 ~ 0 0 0 dBmV
Current System Time: Sun, Jan 17, 2021 18:07:21







Time Priority Description
2021-01-17, 11:03:02 Critical (3) SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=08:36:c9:ce:b3:00;CMTS-MAC=00:01:5c:71:72:67;CM-QOS=1.1;CM-VER=3.1;
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=08:36:c9:ce:b3:00;CMTS-MAC=00:01:5c:71:72:67;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=08:36:c9:ce:b3:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2021-01-17, 08:48:36 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=08:36:c9:ce:b3:00;CMTS-MAC=00:01:5c:71:72:67;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=08:36:c9:ce:b3:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2021-01-17, 08:47:28 Critical (3) Resetting the cable modem due to docsDevResetNow
2021-01-17, 08:46:44 Critical (3) SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=08:36:c9:ce:b3:00;CMTS-MAC=00:01:5c:71:72:67;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=08:36:c9:ce:b3:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2021-01-17, 08:42:10 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=08:36:c9:ce:b3:00;CMTS-MAC=00:01:5c:71:72:67;CM-QOS=1.1;CM-VER=3.1;
2021-01-17, 08:41:53 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=08:36:c9:ce:b3:00;CMTS-MAC=00:01:5c:71:72:67;CM-QOS=1.1;CM-VER=3.1;
2021-01-17, 08:41:53 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=08:36:c9:ce:b3:00;CMTS-MAC=00:01:5c:71:72:67;CM-QOS=1.1;CM-VER=3.1;
2021-01-17, 08:41:08 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=08:36:c9:ce:b3:00;CMTS-MAC=00:01:5c:71:72:67;CM-QOS=1.1;CM-VER=3.1;
2021-01-17, 08:41:07 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=08:36:c9:ce:b3:00;CMTS-MAC=00:01:5c:71:72:67;CM

[remote login] from source fe80::1025:7716:83b:2f5b, Sun, Jan 17, 2021 18:05:39
[admin login] from source 192.168.0.38, Sun, Jan 17, 2021 18:04:22
[DHCP IP: (192.168.0.38)] to MAC address e2:ce:43:82:94:b9, Sun, Jan 17, 2021 18:03:47
[DHCP IP: (192.168.0.3)] to MAC address 00:05:cd:39:fb:e0, Sun, Jan 17, 2021 16:58:06
[Internet connected] IP address: 73.134.72.134, Sun, Jan 17, 2021 16:49:04
[Internet disconnected] Sun, Jan 17, 2021 16:48:35
[Internet disconnected] Sun, Jan 17, 2021 16:48:35
[DHCP IP: (192.168.0.37)] to MAC address d8:0f:99:5f:f5:81, Sun, Jan 17, 2021 16:37:15
[DHCP IP: (192.168.0.35)] to MAC address 0a:93:e2:1b:e8:27, Sun, Jan 17, 2021 16:30:25
[DHCP IP: (192.168.0.34)] to MAC address c8:fd:19:80:ce:95, Sun, Jan 17, 2021 16:06:19
[DHCP IP: (192.168.0.29)] to MAC address 00:7c:2d:2a:45:9e, Sun, Jan 17, 2021 16:05:04
[DHCP IP: (192.168.0.23)] to MAC address 98:84:e3:db:15:61, Sun, Jan 17, 2021 16:04:25

[plemans]

please take a snip as its easier to read/interpret

Open Snipping Tool and take a screenshot (microsoft.com)

[Monte70car]

Here is the screen shots

[Monte70car]

The inserts photo option didn't work so here is the event logs.

[Monte70car]

Got a few more files. Those numbers seem to be all over the place and not what it should be per someone eles post with the same modem.

[Monte70car]

Upstream power.

[plemans]

And no amplifiers in line? Or anything else? 

your upstream power is low and its going to cause issues. 

And you're log is indicating line/power issues. 

[Monte70car]

No amplifiers, no splitters. Straight connection from the outside of the home into the room with the modem/router is at. I asked the ISP tech about turning up the power as I saw where they run it lower and was told they can’t turn up the upstream power. At that point I told the tech he made go because I had already did the research and knew the issues was the power. The reaction I got was it worked the day before what was the power then which was a good question as I had no need to look at it as the network was up. Which could also be why it works and then cuts out like it’s doing right now. At the end I believe we are switching ISP companies and then have to figure out a new way to cover a three floor townhouse with 2550sqft.

[plemans]

What I've had to do with comcast before is to rent a modem from them for a month/2 to prove that it wasn't a modem issue. 

many times they're set that the line is fine. 

but they truly can't just "turn up the upstream power". thats the modem negotiating with the cmts for what power level it needs to use to communicate with it. It could be an issue with the cmts. 

[Monte70car]

For some odd reason we are able to access the internet this morning using the same router. All the settings all the same as when there was no internet.