Empty Custom Nameserver List

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PaulH

PaulH

Member
Dec 21, 2025
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DNS Bench 2, v4 under Win11 25H2.

Try as I might, I am unable to create a custom nameservers list through my Ubiquiti UniFi UDM Pro. The custom nameserver ranking appears to run as expected, taking just under 20 minutes. When it completes, a few nameservers appear in red, then vanish before the “Do you wish to overwrite DNSBENCH.INI?” box. The only nameserver in the list is the Unifi box.

Has anyone else had issues with DNS Bench and a UniFi box? I’d rather not flip options on and off at random until something works (or breaks) with DNS Bench.

I mostly have the recommended settings on the UDM Pro, including the default IPS settings. Unifi OS 4.4.6 and Network 10.0.162. I’m not using the CyberSecure service. I don’t see anything untoward in the log files.

Thanks!

Paul
 
Ubiquiti UniFi UDM Pro = deep packet inspection.

'Feels' like DNSBench can't get the response it expects from an
unfiltered direct link to DNS Servers.
 
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@PaulH Hello from another Paul :) I have a router which offers the option to rewrite UDP queries on the way out to any DNS server that is not my chosen one. This completely breaks the DNSB as it doesn't get the responses it would like, and it actually pops up a warning message thinking it has lost connectivity to the Internet. Perhaps your router is doing something similar. On mine, I can toggle the option off if I want, and when I do, DNSB works just fine. Maybe check for any "creative" DNS related settings in your router and try making some [temporary] changes to see if it makes any difference?
 
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If PHolder is correct, check the firewall rules for anything related to port 53 (DNS can use TCP, BTW).

I only say this because the guide written by Mike (Steve pointed it out in an SN episode) for the Edge Router X had a section where he configured at least one of the vLANs to be forced to use the Edge Router's DNS server, and it was through the firewall. I threw out my UDM when I got my Opnsense box as for whatever reason, my UDM was randomly incompatible with my ISP (Anything over 200MB would drop the connection, and it was on the WAN side this happened because it couldn't even download its own firmware updates of 500+MB without an error)
 
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Thanks for the suggestions, everyone. I've tried switching the various DNS options on the UDM Pro, but the custom list still failed to build.

It appears to be a firewall issue, so when I have some time, I'll review the UDM's firewall options.

I forgot to mention that my ISP is Bell Canada, and it only supports IPv4.
 
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