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Intermittent "DNS not working" or "test site can't be reached" on Xfinity



in Comcast
- For many weeks I've been having intermittent DNS fails, several times a day on my MacBook Pro, connected via Ethernet to the router, via a 24 port switch in the wiring close.
- We have 300mbit service, and a recent Comcast node split, so bandwidth doesn't seem to be the issue. And all the wiring into the house from the pole has been checked.
- In addition, iPhones experience very long load times for apps and web sites, intermittently.
- Comcast is our only local provider. I was using the XB6 gateway with xFi Pods. Tech support didn't offer any ideas for the problem, other than restart. And you can't change the DNS supplier on the XB6, it's locked to Comcast's DNS.
- So I put the XB6 in Bridge mode and setup an Eero Pro as the router, using Comcast DNS. Same problem. So then I went to custom DNS, using Cloudflare 1.1.1.1 as primary and Google 8.8.8.8 as backup for both IPv4 and IPv6.
- Still have the problem.
- Note that I have many smart home devices on the network, in addition to four people's worth of laptops and smartphones, plus extras. So there's lots going on in the network. Three or even four of us using video chat at once.
- But Fing Desktop software will and post DNS fail notices in the middle of the night when we're all sleeping!
- I've got a Fing Box, in addition the Mac app, and the iPhone app.
- no clue on what the cause is.
- Any suggestions?
In addition to alerts from Fing, I'll get long delays in loading a web site, or 30 second pauses in Microsoft Teams video calls.
Tagged:
1
Answers
-Warden Anastasia Luccio, Captain
1.) What DNS IPs? - See line 5 -> "custom DNS, using Cloudflare 1.1.1.1 as primary and Google 8.8.8.8 as backup for both IPv4 and IPv6"
2. What make/model is the router? See line 4 & 5 - XB6 Gateway in bridge mode, Router is Eero Pro, with 2 more Eero Pro as mesh nodes in the house.
3. How old is the router? Eero Pro is from 2016, and is still a shipping model. They update firmware regularly.
New data point, screen shot below.
Eero puts its router address as the first DNS address, 192.168.7.1
Note below that failed. but it got a result from the secondary DNS, Google's 8.8.8.8.
And 30 second outages of streaming video or screen sharing have increased in the last two days.
I will try the suggestions to:
- eliminate the secondary DNS, though not sure how that helps
- get new modem/gateway - Comcast installing an XB7 on Monday. And I hope to try a different mesh router/WiFi system beyond the Eero soon.
- for the 24 hour command line test, I have access to a Mac or PC. Any link to more detailed instructions of what this will look like and how to interpret the results?
- any useful software, beyond Fing, for figuring out what is going on?
Thanks all!
-Warden Anastasia Luccio, Captain