Your message dated Tue, 20 Jan 2026 15:30:27 +0100
with message-id <[email protected]>
and subject line Re: [Pkg-utopia-maintainers] Bug#1125800: network-manager:
Disabling IPv4 manually causes n-m to disconnect after few seconds from IPv6
has caused the Debian Bug report #1125800,
regarding network-manager: Disabling IPv4 manually causes n-m to disconnect
after few seconds from IPv6
to be marked as done.
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If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.
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--
1125800: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1125800
Debian Bug Tracking System
Contact [email protected] with problems
--- Begin Message ---
Package: network-manager
Version: 1.54.3-1+b1
Severity: important
Tags: ipv6
X-Debbugs-Cc: [email protected]
I decided to disable manually IPv4 (DHCP) on the interface via gnome
network manager integration.
Network is dual stacked, but I also did setup NAT64 and DNS64, and
things do work, but IPv4 is still prefered (because network manager does
not support DHCP option 108 - aha PREF64, or it is simply not enabled by
default on debian for some reasons - unclear, I do have lxcbr0 with some
IPv4, but I doubt that this is it).
Similarly n-m puts IPv4 nameservers from DHCPv4 at the top of the
/etc/resolv.conf, so the DNS IPv6 servers that are received via IPv6 RA
that are used for DNS64/NAT64 are later in the chain of nameservers
tried, and in practice are never tried. Thus preventing utilization of
nat64 or IPv6-only network. I know there is ipv{4,6}.dns-priority, but
that must be modified on each host, and cannot be influenced right now
by DHCP or RA, or other easy means I think.
Because I cannot influence this via DHCP (other than by mac address or
also disabling IPv4 for all other hosts in that ethernet broadcast
domain), I decided to switch off IPv4 manually on this host / network
interface.
In gnome shell n-m interfae i simply did set IPv4 to Disabled.
IPv6 still at Automatic.
After offlining interface and putting it back online. (Flipping the
toggle in the gnome shell n-m interface), IPv6 works, but gnome-shell
shows that it is still connecting, and after between 5 to 50 seconds I
got an error popup notification ("Connection failed - Activation of
network connection failed"), and interface is taken down, bringing down
IPv6 too.
During that period nmcli shows:
enp65s0f0np0: connecting (getting IP configuration) to Wired connection 1
"Intel E810-C for QSFP"
ethernet (ice), 64:9D:99:11:22:33, hw, sriov, mtu 1500
ip6 default
DNS configuration:
servers: 2001:cafe:bafe:1::64
domains: foo.example.com
interface: enp65s0f0np0
but inspecting "ip a" shows interface up (ra mtu 9000 is ignored but
that is separate maner), SLAAC addresses assigned, routes and defaults
routes assigned to, and even /etc/resolv.conf listing proper
nameserver(s) and dns search list.
Both DNS, IPv6, and DNS64 / NAT64 work perfectly fine for short time
(between 5 and maybe 120 seconds depending on my luck) - tested with
dig, host, curl, firefox, ping, etc.
After disconnecting nmcli shows:
enp65s0f0np0: disconnected
"Intel E810-C for QSFP"
Router is VyOS 1.5, using radv, with nat64 prefix set too (ignored on
Linux, but usable on Android and iPhone), and other generic options that
work fine if I do not disable IPv4 on the debian desktop machine.
This totally looks like a bug in n-m.
root@debian:~# nmcli con edit f662d320-87ec-3fcf-8c29-17814411099a
...
nmcli> print
===============================================================================
Connection profile details (Wired connection 1)
===============================================================================
connection.id: Wired connection 1
connection.uuid: f662d320-87ec-3fcf-8c29-aabbccddee1099a
connection.stable-id: --
connection.type: 802-3-ethernet
connection.interface-name: enp65s0f0np0
connection.autoconnect: yes
connection.autoconnect-priority: -999
connection.autoconnect-retries: -1 (default)
connection.multi-connect: 0 (default)
connection.auth-retries: -1
connection.timestamp: 1768717797
connection.permissions: --
connection.zone: --
connection.controller: --
connection.master: --
connection.slave-type: --
connection.port-type: --
connection.autoconnect-slaves: -1 (default)
connection.autoconnect-ports: -1 (default)
connection.down-on-poweroff: -1 (default)
connection.secondaries: --
connection.gateway-ping-timeout: 0
connection.ip-ping-timeout: 0
connection.ip-ping-addresses: --
connection.ip-ping-addresses-require-all:-1 (default)
connection.metered: unknown
connection.lldp: default
connection.mdns: -1 (default)
connection.llmnr: -1 (default)
connection.dns-over-tls: -1 (default)
connection.mptcp-flags: 0x0 (default)
connection.wait-device-timeout: -1
connection.wait-activation-delay: -1
-------------------------------------------------------------------------------
802-3-ethernet.port: --
802-3-ethernet.speed: 0
802-3-ethernet.duplex: --
802-3-ethernet.auto-negotiate: no
802-3-ethernet.mac-address: --
802-3-ethernet.cloned-mac-address: --
802-3-ethernet.generate-mac-address-mask:--
802-3-ethernet.mac-address-denylist: --
802-3-ethernet.mtu: auto
802-3-ethernet.s390-subchannels: --
802-3-ethernet.s390-nettype: --
802-3-ethernet.s390-options: --
802-3-ethernet.wake-on-lan: default
802-3-ethernet.wake-on-lan-password: --
802-3-ethernet.accept-all-mac-addresses:-1 (default)
-------------------------------------------------------------------------------
ipv4.method: disabled
ipv4.dns: --
ipv4.dns-search: --
ipv4.dns-options: --
ipv4.dns-priority: 0
ipv4.addresses: --
ipv4.gateway: --
ipv4.routes: --
ipv4.route-metric: -1
ipv4.route-table: 0 (unspec)
ipv4.routing-rules: --
ipv4.replace-local-rule: -1 (default)
ipv4.dhcp-send-release: -1 (default)
ipv4.routed-dns: -1 (default)
ipv4.ignore-auto-routes: no
ipv4.ignore-auto-dns: no
ipv4.dhcp-client-id: --
ipv4.dhcp-iaid: --
ipv4.dhcp-dscp: --
ipv4.dhcp-timeout: 0 (default)
ipv4.dhcp-send-hostname-deprecated: yes
ipv4.dhcp-send-hostname: -1 (default)
ipv4.forwarding: -1 (default)
ipv4.dhcp-hostname: --
ipv4.dhcp-fqdn: --
ipv4.dhcp-hostname-flags: 0x0 (none)
ipv4.never-default: no
ipv4.may-fail: yes
ipv4.required-timeout: -1 (default)
ipv4.dad-timeout: -1 (default)
ipv4.dhcp-vendor-class-identifier: --
ipv4.dhcp-ipv6-only-preferred: -1 (default)
ipv4.link-local: 0 (default)
ipv4.dhcp-reject-servers: --
ipv4.auto-route-ext-gw: -1 (default)
ipv4.shared-dhcp-range: --
ipv4.shared-dhcp-lease-time: 0 (default)
-------------------------------------------------------------------------------
ipv6.method: auto
ipv6.dns: --
ipv6.dns-search: --
ipv6.dns-options: --
ipv6.dns-priority: 0
ipv6.addresses: --
ipv6.gateway: --
ipv6.routes: --
ipv6.route-metric: -1
ipv6.route-table: 0 (unspec)
ipv6.routing-rules: --
ipv6.replace-local-rule: -1 (default)
ipv6.dhcp-send-release: -1 (default)
ipv6.routed-dns: -1 (default)
ipv6.ignore-auto-routes: no
ipv6.ignore-auto-dns: no
ipv6.never-default: no
ipv6.may-fail: yes
ipv6.required-timeout: -1 (default)
ipv6.ip6-privacy: -1 (default)
ipv6.temp-valid-lifetime: 0 (default)
ipv6.temp-preferred-lifetime: 0 (default)
ipv6.addr-gen-mode: default
ipv6.ra-timeout: 0 (default)
ipv6.mtu: auto
ipv6.dhcp-pd-hint: --
ipv6.dhcp-duid: --
ipv6.dhcp-iaid: --
ipv6.dhcp-timeout: 0 (default)
ipv6.dhcp-send-hostname-deprecated: yes
ipv6.dhcp-send-hostname: -1 (default)
ipv6.dhcp-hostname: --
ipv6.dhcp-hostname-flags: 0x0 (none)
ipv6.auto-route-ext-gw: -1 (default)
ipv6.token: --
-------------------------------------------------------------------------------
proxy.method: none
proxy.browser-only: no
proxy.pac-url: --
proxy.pac-script: --
-------------------------------------------------------------------------------
-- System Information:
Debian Release: forky/sid
APT prefers testing-debug
APT policy: (500, 'testing-debug'), (500, 'unstable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386
Kernel: Linux 6.19.0-rc1 (SMP w/32 CPU threads; PREEMPT)
Kernel taint flags: TAINT_CPU_OUT_OF_SPEC, TAINT_UNSIGNED_MODULE
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
Versions of packages network-manager depends on:
ii adduser 3.153
ii dbus [default-dbus-system-bus] 1.16.2-2
ii libaudit1 1:4.1.2-1+b1
ii libbluetooth3 5.84-1
ii libc6 2.42-7
ii libcurl3t64-gnutls 8.18.0~rc2-1
ii libglib2.0-0t64 2.86.3-1
ii libgnutls30t64 3.8.11-3
ii libjansson4 2.14-2+b4
ii libmm-glib0 1.24.2-2
ii libndp0 1.9-1+b1
ii libnewt0.52 0.52.25-1+b1
ii libnm0 1.54.3-1+b1
ii libpsl5t64 0.21.2-1.1+b1
ii libreadline8t64 8.3-3
ii libselinux1 3.9-4+b1
ii libsystemd0 259-1
ii libteamdctl0 1.31-1+b3
ii libudev1 259-1
Versions of packages network-manager recommends:
ii dnsmasq-base [dnsmasq-base] 2.92~rc3-1
ii libpam-systemd 259-1
ii modemmanager 1.24.2-2
ii network-manager-l10n 1.54.3-1
ii polkitd 127-1
ii ppp 2.5.2-1+1.1
ii udev 259-1
ii wireless-regdb 2025.10.07-1
ii wpasupplicant 2:2.10-25
Versions of packages network-manager suggests:
ii iptables 1.8.11-4
ii libteam-utils 1.31-1+b3
Versions of packages network-manager is related to:
pn isc-dhcp-client <none>
-- no debconf information
--- End Message ---
--- Begin Message ---
Am 19.01.26 um 21:47 schrieb Witold Baryluk:
Package: network-manager
Followup-For: Bug #1125800
X-Debbugs-Cc: [email protected]
Dear Maintainer,
please close this bug report.
Beniamino Galvani, a Network Manager contributor / developer looked into
it, and said that this is because I am receiving two RAs, and one of
them says to use DHCPv6 (managed flag is set), then n-m tries, but it
fails (I do not run DHCPv6), and after timeout considers connection bad,
and disconnects.
This was caused by bad default configuration (or misconfiguration many
many years ago), on one of non-routing WiFi access points running in the
same network. Disconnecting that WiFi access point, solved the problem.
So probably not a bug in network manager.
I will later see and check RFCs what host should do when receiving exact
packets I presented in tcpdump in my previous message (one with no
routes, and medium prio, but with managed flag set, and another with
routes, high prio, dns options and no managed flag set).
Please close.
Thanks or the update.
Closing accordingly.
Michael
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--- End Message ---
