Debugging issues

I have been using Cloudflare DNS for over 6 months. Pretty regularly, we have network problems and I have been trying to debug them. First, here’s my network set up.

Given that I can’t control all variables (e.g. Comcast issues), I have tried several things to debug when we have problems.

  1. Several times had ISP (Comcast) check that our connection is good. Strong signal and no history they can find of problems with signal, etc.
  2. Automated daily reboots of modem to make sure that we start with a fresh connection every day before we wake up.
  3. Replaced the modem a while back. Can’t remember if that was before moving to Cloudflare for DNS or not. It may have been.
  4. Try different devices to eliminate the device itself as the problem.
  5. Made sure to test on wired connections to eliminate wifi issues.
  6. When trouble comes up, sometimes I just switch DNS to either Google or Comcast and poof, problem goes away.
  7. I have tried taking various devices such as cujo out of the loop and changing nothing else. This doesn’t seem to have an effect.
  8. Today, I tried putting Cloudflare (1.1.1.1) as our primary DNS server and Comcast as a secondary. So far far so good but too soon to tell.
  9. Problems are not isolated to particular times of the day. Nothing consistent that I can identify as being a likely culprit.

This is incredibly inconvenient and frustrating. Networks shouldn’t be so fragile. I’m not sure how else to completely isolate what the issue might be. I don’t want to point the finger incorrectly and Cloudflare stats are excellent so I find it hard to believe that it is down anywhere near as often as we have problems.

What does a traceroute say?

Things are working fine at the moment. Here’s a trace to YouTube.

#1
- RTT [ms]: 2.1
- Probe Send Time: 6:07:38 PM
- IP Address: 192.168.0.1
- TTL: 64

#2
- RTT [ms]: 11.3
- Probe Send Time: 6:07:38 PM
- IP Address: 96.120.89.141
- TTL: 63
- AS Number: AS7922
- AS Name: Comcast Cable Communications, LLC
- Country Name: United States
- Country Code: US

#3
- RTT [ms]: 12.9
- Probe Send Time: 6:07:38 PM
- IP Address: 68.85.216.13
- Hostname: be-20005-rur02.santaclara.ca.sfba.comcast.net
- TTL: 253
- AS Number: AS7922
- AS Name: Comcast Cable Communications, LLC
- Country Name: United States
- Country Code: US

#4
- RTT [ms]: 11.2
- Probe Send Time: 6:07:38 PM
- IP Address: 162.151.78.129
- TTL: 253
- AS Number: AS7922
- AS Name: Comcast Cable Communications, LLC
- Country Name: United States
- Country Code: US

#5
- RTT [ms]: 11.5
- Probe Send Time: 6:07:38 PM
- IP Address: 162.151.78.253
- Hostname: be-232-rar01.santaclara.ca.sfba.comcast.net
- TTL: 252
- AS Number: AS7922
- AS Name: Comcast Cable Communications, LLC
- Country Name: United States
- Country Code: US

#6
- RTT [ms]: 10.9
- Probe Send Time: 6:07:39 PM
- IP Address: 68.86.143.93
- Hostname: be-299-ar01.santaclara.ca.sfba.comcast.net
- TTL: 251
- AS Number: AS7922
- AS Name: Comcast Cable Communications, LLC
- Country Name: United States
- Country Code: US

#7
- RTT [ms]: 14.3
- Probe Send Time: 6:07:39 PM
- IP Address: 96.112.146.22
- TTL: 55
- AS Number: AS7922
- AS Name: Comcast Cable Communications, LLC
- Country Name: United States
- Country Code: US

#8
- Probe Send Time: 6:07:39 PM

#9
- RTT [ms]: 13.4
- Probe Send Time: 6:07:40 PM
- IP Address: 72.14.235.2
- TTL: 56
- AS Number: AS15169
- AS Name: Google LLC
- Country Name: United States
- Country Code: US

#10
- RTT [ms]: 18.7
- Probe Send Time: 6:07:41 PM
- IP Address: 108.170.242.238
- TTL: 248
- AS Number: AS15169
- AS Name: Google LLC
- Country Name: United States
- Country Code: US

#11
- RTT [ms]: 21.9
- Probe Send Time: 6:07:41 PM
- IP Address: 74.125.253.190
- TTL: 247
- AS Number: AS15169
- AS Name: Google LLC
- Country Name: United States
- Country Code: US

#12
- RTT [ms]: 20.8
- Probe Send Time: 6:07:41 PM
- IP Address: 72.14.237.146
- TTL: 248
- AS Number: AS15169
- AS Name: Google LLC
- Country Name: United States
- Country Code: US

#13
- RTT [ms]: 13.3
- Probe Send Time: 6:07:41 PM
- IP Address: 108.170.242.241
- TTL: 247
- AS Number: AS15169
- AS Name: Google LLC
- Country Name: United States
- Country Code: US

#14
- RTT [ms]: 14.9
- Probe Send Time: 6:07:42 PM
- IP Address: 209.85.248.35
- TTL: 55
- AS Number: AS15169
- AS Name: Google LLC
- Country Name: United States
- Country Code: US

#15
- RTT [ms]: 12.4
- Probe Send Time: 6:07:42 PM
- IP Address: 172.217.6.78
- Hostname: sfo07s17-in-f78.1e100.net
- TTL: 54
- AS Number: AS15169
- AS Name: Google LLC
- Country Name: United States
- Country Code: US

If you want a Plan B, set your DNS to 1.0.0.1 instead of 1.1.1.1. Let that run for a period of time. Or wait until a failure and then switch to 1.0.0.1 instead of Google or Comcast.

2 Likes

I should have clarified that I always had two servers set, never one. Usually 1.1.1.1 and 1.0.0.1 as the fallback. My modem doesn’t let me configure more than two servers. By habit I’m had always set primary and secondary to the same provider.

Then there is nothing to debug :wink:

You’ll need to collect that information once it is not working again and only then one might be able to say more based on it.

Heh, well it is unusual to have to set DNS to two separate providers.

I wouldnt consider it unusual as I have such a setup too, but thats a different topic anyhow. We’d need to find out where the connection stops when it stops.

Agreed. You are right, next step is to see if the problem returns. If after a few days or so there are no problems maybe I’ll switch the secondary DNS server to 1.0.0.1 and see if problems return.