Custom DNS is not working

[Apolloborn]

Using the Google Home app, I have navigated to Wifi advanced DNS settings and set the IPv4 and IPv6 primary and secondary addresses for OpenDNS as my custom DNS. I have reentered them several times and have been sure to hit the "Save" icon. All of the devices on my network are reporting the Google Wifi hub (192.168.1.1) as their configured DNS server, which is as expected. 

No matter what I do, all signs point to my computers still using my ISP's DNS (Comcast). I have flushed my computer's DNS cache and rebooted all of the Google Wifi points. I have verified this using What's My DNS Server (https://www.top10vpn.com/tools/what-is-my-dns-server/) and the OpenDNS test page (http://welcome.opendns.com), testing with both my browser (after clearing the cache) and the nslookup command line. 

I am stumped. Any ideas what else I should try?

[MichaelP]

Hello @Apolloborn 

Hmm. So, the way this works is that all of the DNS requests will still be sent to the primary Google WiFi unit, but the custom DNS server addresses you've configured will then be where that resolver sends the requests. I use custom DNS servers inside my network, and I can see they get plenty of DNS requests – they're just all coming from my primary Google WiFi unit (on behalf of the clients on my network). My servers then forward requests back out to Google's DNS servers via DNS-over-HTTPS. The "What's My DNS Server" link you posted above showed Google as being my DNS server, so it seems to all be working for me. In your case, you don't have custom internal DNS servers, but are just pointing Google WiFi directly at OpenDNS. I haven't done that, but unless Comcast is blocking traffic to those servers, it should "just work". Have you tried switching to something like Google's DNS servers, or maybe Cloudflare's (1.1.1.1) just to test it out? If that works (checking with the first link you included), then you can start to home in on why OpenDNS isn't working.

[Apolloborn]

Yes I did try switching to Cloudflare at one point in the past and similarly couldn't get it to work. I can manually configure each device to point to OpenDNS servers, but that is both frustrating to have to do and impractical for some of my IoT devices. 

I would like it to work as it is advertised to work: my devices use my Google Wifi router as their DNS (192.168.1.1), and the router acts as a cache for the custom DNS servers (OpenDNS). 

My Comcast Xfinity router (unsurprisingly) is configured to use Comcast's DNS servers and that can't be changed. But that router is on its own subnet (10.0.0.X) and its DHCP/DNS advertisements are not affecting devices on my Google Wifi network. 

[MichaelP]

That is puzzling. It sounds like your Google WiFi router is inside the network created by your Comcast modem+router – I wonder if that outer router is causing the issue here? I know Google WiFi can use custom DNS servers, so I'm trying to understand what could be different about your situation.

[EdwardT]

Hi folks,

@MichaelP, thanks for the help!

@Apolloborn, how's it going with your Google WiFi? Still need our help?

Thanks,

Edward

[Apolloborn]

Yes, nothing has changed despite my trying countless settings permutations. I am still stuck with Comcast's DNS servers even though my Google Wi-Fi is clearly set to use OpenDNS servers in custom DNS settings.

[Jeff]

Hi, Apolloborn.

It's been a while since we checked in here so I wanted to see if you were still seeing the same issues here or if you were able to work it out. If things are still not right, please let me know and we can pick troubleshooting back up.

Thanks.

[Apolloborn · Accepted solution]

Hi Jeff! I rebuilt my entire network to install an additional ISP in a load balanced WAN configuration. In the process, I factory reset the Google Wifi points. Lo and behold, when I entered the custom DNS settings after the reset, they worked this time.

I guess all systems need a clean reboot every once in a while. Thanks for your willingness to try to help!

[Jeff]

Hi, Apolloborn.

Thanks for letting me know you got things working correctly. That's great news! I'll go ahead and mark this as resolved, but if you need anything else going forward, please feel free to open up a new thread.

Thanks again!