Updating from 15.2 to 15.3 Broke UDP Across Subnets

[Ducky6944]

• Unifi Network with no block udp/multicast, or isolate networks settings.
• Running via docker on debian
• Using a macvlan
• Using defaults for technitium
• Using the supplied docker compose
• no settings changes between the versions or updates of the host or network between the update

on 15.3
from 10.0.100.x dig google.com @10.0.100.8 produces a record
from 10.0.x.x dig google.com @10.0.100.8 times out
from 10.0.x.x nslookup google.com 10.0.100.8 time out
from 10.0.x.x nslookup -vc google.com 10.0.100.8 immediate reply

on 15.2
from 10.0.x.x dig google.com @10.0.100.8 produces a record.

I apologize for the less than satisfactory bug report. I am out of my element in networking. I am happy to provide anything needed.

[joshuaprince]

+1, I'm seeing something very similar after upgrading to 15.3.

I have an AdGuard Home container pointing to Technitium as its upstream DNS resolver. AdGuard Home runs with bridged networking (172.21.x.x), Technitium runs with host networking (10.2.x.x). On the AGH side, I see a mixture of timeouts and refused connections to Technitium:

2026/07/08 01:58:31.542761 [error] dnsproxy: exchange failed upstream=10.2.2.4:53 question=";stun.schlund.de.\tIN\t AAAA" duration=10.000187218s err="exchanging with 10.2.2.4:53 over udp: read udp 172.21.0.2:41577->10.2.2.4:53: read: connection refused"
2026/07/08 01:58:31.926035 [error] dnsproxy: response received upstream_type=main addr=10.2.2.4:53 proto=udp status="exchanging with 10.2.2.4:53 over udp: read udp 172.21.0.2:41323->10.2.2.4:53: i/o timeout"

Likewise, from inside another bridge-mode container that supports dig, Technitium refuses its requests:

# dig @10.2.2.4 google.com
;; communications error to 10.2.2.4#53: connection refused
;; communications error to 10.2.2.4#53: connection refused
;; communications error to 10.2.2.4#53: connection refused

; <<>> DiG 9.18.39-0ubuntu0.24.04.5-Ubuntu <<>> @10.2.2.4 google.com
; (1 server found)
;; global options: +cmd
;; no servers could be reached

Thank you for the great DNS server!

[ShreyasZare]

Thanks for the feedback. An update is coming very soon to fix few similar issues that were reported. Will let you know when the update is available.

[senwebtek]

I'm having a similar issue with udp requests coming from docker. The connection is refused with udp but the same dns request over tcp works.