mDNS stopped working in WSL2 after Windows 11 Pro update

[jtgoral]

Windows Version

Microsoft Windows [Version 10.0.22635.3061]

WSL Version

2.1.0.0

Are you using WSL 1 or WSL 2?

• WSL 2
• WSL 1

Kernel Version

5.15.137.3-1

Distro Version

Ubuntu 23.10

Other Software

No response

Repro Steps

ping okno-t320.local does not find okno-t320

Expected Behavior

jacek@okno-galaxy:~$ ping 192.168.68.115
PING 192.168.68.115 (192.168.68.115) 56(84) bytes of data.
64 bytes from 192.168.68.115: icmp_seq=1 ttl=63 time=7.53 ms
64 bytes from 192.168.68.115: icmp_seq=2 ttl=63 time=5.69 ms
64 bytes from 192.168.68.115: icmp_seq=3 ttl=63 time=6.20 ms
^C
--- 192.168.68.115 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2005ms
rtt min/avg/max/mdev = 5.689/6.472/7.533/0.777 ms

Actual Behavior

jacek@okno-galaxy:$ ping okno-t320.local
ping: okno-t320.local: Name or service not known
jacek@okno-galaxy:$

Diagnostic Logs

No response

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[jtgoral]

I forgot to add that it happened on 2 windows computers after the same update.

[jtgoral]

When running from Windows Power Shell ping works ok. From WSL2 no more.

[ghost]

Are you sure this has anything to do with windows update? What do you have in /etc/nsswitch.conf?

[OneBlue]

Thank you @jtgoral. Can you try to put the following in %userprofile%/.wslconfig, then run: "wsl.exe --shutdown" to apply them:

[wsl2]
dnsTunneling=false

And see if that solves the issue ?

[jtgoral]

Yes, Adding the line to .wslconfig solved the problem on both computers:

jacek@okno-galaxy:/mnt/c/Users/jacek/public_html/beer/beersmith2$ ping okno-t320.local
PING okno-t320.local (192.168.68.115) 56(84) bytes of data.
64 bytes from 192.168.68.115 (192.168.68.115): icmp_seq=1 ttl=63 time=14.9 ms
64 bytes from 192.168.68.115 (192.168.68.115): icmp_seq=2 ttl=63 time=16.4 ms

[jtgoral]

Yes, it was caused by a Windows update. All tries to use avahi connections stopped working right after the update on two Windows boxes.. Computers I connect from WSL (*.local) are FreeBSD and EndeavourOS Linux.
Modifying .wslconfig as suggested fixed the problem and my git repository, ssh and VNC servers are available again when using .local instead of IP addresses.

[andybarron]

i also had this issue on the most recent version of Windows 11 Pro (as of 2024-06-14). the suggested fix worked for me as well.

[dannystaple]

I can confirm that the workaround from @OneBlue worked for me too.

[Davidonium]

I can also confirm that the upgrade broke this for me and what @OneBlue suggested fixed the issue.
I tried adding that configuration value inside the distribution's /etc/wsl.conf file and it didn't work, so adding that configuration on %userprofile%/.wslconfig in the host machine is the only way.

[gkuga]

I used to be able to resolve names in the .local domain, but recently I encountered this issue.
For my case, the following fixes were necessary:

# the workaround from @OneBlue 
[wsl2]
dnsTunneling=false

# /etc/nsswitch.conf
-hosts:          files mdns4_minimal [NOTFOUND=return] dns
+hosts:          files dns mdns4_minimal

(I am using WSL2 in NAT mode not Mirrored mode.)

[NelsonMinar]

I just re-discovered this problem and fix of disabling DNS tunneling. It seems like a pretty significant regression in WSL2, for .local domains to just stop working in the default configuration. Is this a temporary bug in the DNS tunneling implementation, will it eventually start working with mDNS again?

[benhillis]

@CatalinFetoiu & @keith-horton - could you please take a look?

[gitcnd]

I "solved" this by running a perl DNS server on a centos host on the same network, which calls avahi-resolve -n whatever.local and outputs the IP, which it gives to "bind" (named) which is set up as a caching nameserver. Annoying I had to do this, but I have a lot of WSL machines and this was really getting in the way of my IoT development...

// named.conf
//
// Provided by Red Hat bind package to configure the ISC BIND named(8) DNS
// server as a caching only nameserver (as a localhost DNS resolver only).
//
// See /usr/share/doc/bind*/sample/ for example named configuration files.
// see also https://bind9.readthedocs.io/en/latest/chapter6.html
//

options {
        listen-on port 53 { 192.168.1.66; };
        listen-on-v6 port 53 { ::1; };
        directory       "/var/named";
        dump-file       "/var/named/data/cache_dump.db";
        statistics-file "/var/named/data/named_stats.txt";
        memstatistics-file "/var/named/data/named_mem_stats.txt";
        secroots-file   "/var/named/data/named.secroots";
        recursing-file  "/var/named/data/named.recursing";
        allow-query     { localhost; 192.168.1.0/24; };

        recursion yes;

        dnssec-validation no;

        managed-keys-directory "/var/named/dynamic";
        geoip-directory "/usr/share/GeoIP";

        pid-file "/run/named/named.pid";
        session-keyfile "/run/named/session.key";

        /* https://fedoraproject.org/wiki/Changes/CryptoPolicy */
        include "/etc/crypto-policies/back-ends/bind.config";
};

logging {
        channel default_debug {
                file "data/named.run";
                severity dynamic;
        };
};

zone "." IN {
        type hint;
        file "named.ca";
};

zone "local" {
    type forward;
    forward only;
    forwarders { 127.0.0.1; };
};

include "/etc/named.rfc1912.zones";
include "/etc/named.root.key";

[CatalinFetoiu]

thanks for reporting the issue

we have updated the docs to include details about how to resolve .local names in WSL. Please refer to https://learn.microsoft.com/en-us/windows/wsl/troubleshooting#resolve-local-names-in-wsl

let us know if you have any questions

[NelsonMinar]

tl;dr: the new docs suggest turning off DNS tunneling and using mirrored networking mode.

[shaver]

and netgroup: nis, for old time's sake

(more constructively, it would be great if there were a header list of the common issues, and if that section linked to something on how to change the networking mode!)

[CatalinFetoiu]

@NelsonMinar if you use mirrored networking mode you can also keep DNS tunneling enabled
We only recommend turning off DNS tunneling if you are using NAT networking mode and want to resolve .local names

[shaver]

I will say that the description of dnsTunneling on https://learn.microsoft.com/en-us/windows/wsl/wsl-config#wslconfig leaves something to be desired. It's basically impossible to tell from the description what it does, such as "make mDNS resolution work", but ideally a more detailed description given that the audience for wsl2 docs likely skews both technically-savvy and curious

Changes how DNS requests are proxied from WSL to Windows

[shaver]

I've executed a wsl --shutdown after changing %UserProfile/.wslconfig and still no dice:

OS Build: 22631.4037
Experience: Windows Feature Experience Pack 1000.22700.1027.0

[CatalinFetoiu]

@shaver please make sure to follow the steps from https://learn.microsoft.com/en-us/windows/wsl/troubleshooting#resolve-local-names-in-wsl, section "networkingMode set to Mirrored"

(make sure to update WSL to the latest pre-release build (2.3.17) and do the configuration mentioned in the docs for enabling mdns in Linux)

[shaver]

thank you, I didn't realize I still had .14 installed!

so, it works now, but there's about a 10 second lag in resolution for either IPv6 or IPv4

[shaver]

@CatalinFetoiu should I open a separate bug for the lag? Happy to do so!

[CatalinFetoiu]

@shaver thanks for testing the fix and following up

yes, please feel free to open a separate issue for the delay you observed

[s73v3r]

I'm still unable to get this to work, despite following the instructions on the Microsoft docs site.

[CatalinFetoiu]

@s73v3r thanks for following up

can you please share the output of sudo strace -ff ping ender6printer.local?
please also collect networking logs using https://github.com/microsoft/WSL/blob/master/diagnostics/collect-networking-logs.ps1, using instructions at https://github.com/microsoft/WSL/blob/master/CONTRIBUTING.md#collect-wsl-logs-for-networking-issues

[21paradox]

i ended up with custom code to find ip address. because i have wifi and wifi hot-spot both connected to another pc. i tried mirror mode but i cannot make a ping to global network again. my laptop is window11 home.

IP=$(echo "require('dnssd/lib/resolve').resolve4('nixos12700.local', {interface: 'WLAN'}).then(console.log)" | '/mnt/c/Program Files/nodejs/node.exe')

[anil-sezer]

This solution fixed it for me.

[YAmikep]

I have the following in my .wslconfig file

[wsl2]
dnsTunneling=false

I even restarted my computer to be sure but I still have issues pinging .local addresses from WSL (it works from powershell).
Any other ideas I can try?

WSL version: 2.3.17.0
Kernel version: 5.15.153.1-2
WSLg version: 1.0.64
MSRDC version: 1.2.5326
Direct3D version: 1.611.1-81528511
DXCore version: 10.0.26100.1-240331-1435.ge-release
Windows version: 10.0.22631.4037

---

UPDATE

I am wondering if the problem is linked to IPV6 because I can directly ping the IPV4 address but not the IPV6 address from WSL and I think the name resolution returns the IPV6 address.

Ping from Powershell using:

• IPV4: ✅
• IPV6: ✅

Ping from WSL using:

• IPV4: ✅
• IPV6: ❌

[CatalinFetoiu]

@YAmikep in order to have IPv6 connectivity in WSL you need to enable mirrored mode - you need to add "networkingMode=mirrored" in your wslconfig file

if you do that, you no longer need to disable DNS tunneling in order to resolve .local names

but you need to follow the steps documented at https://learn.microsoft.com/en-us/windows/wsl/troubleshooting#resolve-local-names-in-wsl (install libnss-mdns and configure /etc/nsswitch.conf) to enable Linux to use mDNS queries

let us know know if you have any questions

[YAmikep]

Thank you @CatalinFetoiu I will try this but I'm also interested in making things work in the NAT mode. Any idea why disabling DNS tunneling does not fix it like it did for some people?

[CatalinFetoiu]

@YAmikep I see, thanks for following up. Please collect networking logs using https://github.com/microsoft/WSL/blob/master/diagnostics/collect-networking-logs.ps1 from the case with NAT mode and dnsTunneling=false and we can take a look

[YAmikep]

@CatalinFetoiu

Ok thanks, I am going to try to collect these logs.
To make sure I am working with the right setup, though, I'd like to clarify what I need to have .local names resolution work on WSL in theory?
Both avahi-daemon and libnss-mdns installed in the WSL distro?

[CatalinFetoiu]

@YAmikep if you are in NAT networking mode, you don't need to install those, but you need to disable DNS tunneling

if you are in mirrored networking mode, you can install libnss-mdns and configure /etc/nsswitch.conf as shown in https://learn.microsoft.com/en-us/windows/wsl/troubleshooting#resolve-local-names-in-wsl

[w00dst0ck]

I use Ubuntu 24.04.1 as my distribution and have found the following solution without using avahi-daemon and libnss-mdns.

Make the following adjustments in the files mentioned

#.wslconfig
dnsTunneling=false

#/etc/wsl.conf
[boot]
systemd=true

[network]
hostname=wsl
generateResolvConf = false

Do not forget to restart the WSL with wsl.exe --shutdown for the adjustments to take effect.

In order to have systemd/resolved use mdns, two more steps are necessary:

1. DNS=x.x.x.x and multicastDNS=yes must be put into /etc/systemd/resolved.conf and resolved restarted to enable it in general.

2. it must be enabled per interface. On the command line this can be done with
   resolvectl mdns eth0 yes

The activation of mDNS for the individual interfaces can then be checked with the command resolvectl mdns.