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19 Messages
Cannot use some websites without rebooting Arris modem/router combo (DNS_PROBE_FINISHED_NXDOMAIN)
We are currently having a very strange, somewhat frustrating issue on our Xfinity home WiFi network. All throughout the last few days (1-30-2020 to 2-1-2020) we will slowly lose the ability to connect to certain and seemingly unrelated websites. It will usually start with Google, which when connecting to it will give the error "DNS_PROBE_FINISHED_NXDOMAIN". Soon we won't be able to see YouTube thumbnails or comments. Then the videos won't even buffer. Eventually that gives a "No Internet" error. Sites like imgur and Reddit are available for a long time but cannot be loaded after enough time. Rebooting our Arris modem/router will fix this but only for a limited time. Four hours or so is all it takes to return to our "no internet" issues. We can live with this but, surely, rebooting our modem four or five times a day is not a true solution.
Before I get to attempted solutions let me list some information about our network.
*Performance Pro+ Internet Package (175 Mbps Downloads)
*Arris Surfboard SBG7400AC2 (router & modem)
* DHCP enabled for both IPV4 and IPV6
* 2.4 GHz & 5 GHz enabled
* DNS Override Enabled (Primary: 1.1.1.1, Secondary: 1.0.0.1, Tertiary: 8.8.8.8|Similar IPs for IPV6)
All but one device, a Windows PC, use Chrome for their web browser. Android Phones and Windows PCs alike encounter the same issues. Both Firefox and Chrome have the exact same results.
Three PCs use the Origin, Steam, and Uplay web clients for games. Every client will eventually report that they are offline and cannot download games or display web pages.
So far I have rebooted the gateway through both the built-in user interface and the Xfinity website. I have disabled DNS override, changed the DNS IPs to be Google's 8.8.8.8/8.8.4.4, and manually changed them to Xfinity's own 75.75.75.75 / 75.75.76.76. And finally, with few ideas left, I tried pulling the power plug and waiting five minutes in the hopes that the device just needed a moment to cool down and a hard reboot.
DNS changes have no effect. Reboots all have the same result. We are able to access all websites without any issues for a few hours before we slowly, one by one, lose access to certain websites. It is very strange to lose Google while researching the issue but still being able to use DuckDuckGo to continue the research. As I type I have lost access to even that yet am able to use any Xfinity sites. I'll be contacting Xfinity support Monday but I was hoping to get these issues fixed before then.
Accepted Solution
BruceW
Gold Problem Solver
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26K Messages
5 years ago
The signal levels look good, but the "SYNC Timing" and "RCS Partial Service" errors in the log suggest a problem with the connection to Comcast's network. Also, the Uncorrectable error counts are very high for a device which has just been restarted.
The SBG7400 may be failing, although signal problems are more likely. These are often due to loose, damaged, or corroded coax or coax connectors, usually in or near your home. If you can't find the problem or you'd rather have Comcast take care of it, call them 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.
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BruceW
Gold Problem Solver
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26K Messages
5 years ago
Are you connecting via Wifi or Ethernet? If Wifi, it's best to switch to an Ethernet cable connection if possible for testing. That would allow you to determine whether the problem is the Wifi signal or the link between your equipment and Comcast's network. Network connection problems that affect both Ethernet and Wifi devices are often due to poor coax connections, usually in or near your home.
If you want to troubleshoot this yourself, please see Connection Troubleshooting Tips. If you still need help, please provide Information Requested for Connection-Related Posts, especially downstream power levels and SNR, upstream power levels, and error log.
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KA_Sant
Frequent Visitor
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19 Messages
5 years ago
It seems as though I took too long gathering information. I restarted the modem again and used imgur instead.
Downstream: https://i.imgur.com/4FOY3JT.png
Upstream: https://i.imgur.com/bAvppJf.png
Event Log: https://i.imgur.com/RJDA1oa.png
Device Status: https://i.imgur.com/jiuFhFU.png
Modem/Router Settings: https://i.imgur.com/l8pKHjP.png
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KA_Sant
Frequent Visitor
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19 Messages
5 years ago
I really appreciate the help and apologize for not providing the correct information before. Here is all of the information requested in a few images. As well as those I have collected some information from my WAN, LAN, and wireless settings that might also help. Those settings were typed out in a text document but I have taken a snip of that to keep things as tidy as I can. I will be attempting to test an ethernet connection soon but I do not have a PC close enough to our modem at the moment. All coax cables I can access have been tightened but issues persist. A Comcast technician will need to be requested to check any other connections.
Downstream
Upstream
Event Log
Device Status
WAN, LAN, and Wireless Settings
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douginsaltlake
New Poster
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1 Message
5 years ago
I'm having the same issue as you are with an Arris SBG7600 AC2 Modem/Router. Started a little over a week ago on the same model of modem I bought used off Amazon. Thought it was the modem so I sent it back and bought a brand new one from Best Buy but I'm having the same issues again. I guess I'll do some more research online.
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BruceW
Gold Problem Solver
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26K Messages
5 years ago
The images you posted aren't visible. They all look like this:
This is probably because the images require moderator approval. That could take a while. You could upload the images to a file sharing site and post links to them here, or post text instead of an image.
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KA_Sant
Frequent Visitor
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19 Messages
5 years ago
I have attempted a few live agent chats to see if our issues could be resolved without a technicians' visit but it seems as though not much could be done from Xfinity's end. In fact, as I type I am having another "DNS_PROBE_FINISHED_NXDOMAIN" error with oauth.xfinity.com and only that site for the moment.
A visit has been scheduled to see if they can find any physical issues with coax cables or other hardware. If any other users find their way here I suggest you do the same. Thank you @BruceW for all of your help and time.
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BruceW
Gold Problem Solver
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26K Messages
5 years ago
Thanks for posting your results. It surprises me that their systems don't distinguish between the two models and automatically load the correct files.
Glad you got it resolved!
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KA_Sant
Frequent Visitor
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19 Messages
5 years ago
One final post for the resolution to my problems before I let this thread go dormant.
The issue turned out to be an error with the modem itself but it wasn't damaged. The tech that came out said the issue was primarily with the modem using the incorrect software to boot. I interpreted this to be the bootcode as that is all I can see in the router's settings but I cannot confirm it as I did not screenshot that beforehand.
I had changed out two different modems in the span of only a month when I first replaced our Xfinity modem and I assume my first, much more weak, modem was still in Xfinity's system. I should have known this when I went to "https://www.xfinity.com/support/devices/#search" and had been told I was using an Arris SBG6700-AC instead of my SBG7400-AC2. The answer to the problem was right in front of my face.
The solution was fairly simple. The tech somehow marked that device as no longer being in use, re-authorized our cable and internet, and finally installed a noise filter on our internet coax cable. BruceW was correct with it being a hardware issue!
If you find yourself here and all of this sounds like the symptoms of your own internet connection troubles consider asking an agent over the phone if you have two modems activated on your account. If you do, ask to remove the older modem and ask for a complete re-authorization of your cable signal. Our WiFi is now up, stable, and super quick again.
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