Seeking diagnostic strategy for single device that may be blocked from internet by new B One router

[Barry_Twycross1250]

I just skimmed this thread, but there’s issues with Quad9 and DoH, they retired http/1.1 which is the only thing Peplink supports.

Quad9 DOH HTTP/1.1 protocol retirement

I’ve been using the Surf SOHO MK3 (F/W 8.3.0) setup to use a proxy DNS server for my home network. As such, I’ve chosen to use Quad9’s DNS over HTTPS service and for the past several years, it’s worked flawlessly. Quad9 is preferred over the various other DOH service providers mainly for their strict privacy policy. On Dec 15th, Quad9 retired the use of HTTP/1.1 in favor of using the newer HTTP/2 transport protocol for all their DOH services … ref: DOH HTTP/1.1 Retirement December 15, 2025 | Q…

The question for me would then be if the B One is failing as a DNS proxy, why are your other devices working.

When you gave the initial problem, my first thought was the DNS tab in the network settings. I’ve had similar issues with McBooks, when I leave a DNS entry in there by mistake.

My debugging would be using tcpdump on the MacBook, and packet capture on the B One (from the hidden support page). If you get the B One to capture packets, they can be interpreted by tcpdump on the Mac, it’s a surprisingly powerful tool.