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#1 2025-05-17 17:10:55

opotonil
Member
Registered: 2009-09-12
Posts: 45

IPv6 fail on wired network and work on wireless network

In my PC (Gnome NetworkManager) with the enabled wired network and the disabled wireless network does not work IPv6:

# ping -c 3 google.com
PING google.com (2a00:1450:4003:802::200e) 56 data bytes

--- google.com ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 2051ms
# tracepath google.com
 1?: [LOCALHOST]                        0.043ms pmtu 1500
 1:  no reply
 2:  no reply
 3:  no reply
 4:  no reply
 5:  no reply

Looking at the routes, I have a default route through the local-link (fe80::xxxx:xxxx:xxxx:60c0):

# ip -6 route show
[...]
default via fe80::xxxx:xxxx:xxxx:60c0 dev enp4s0 proto ra metric 20100 pref medium
# ping -c 3 fe80::xxxx:xxxx:xxxx:60c0%enp4s0
PING fe80::xxxx:xxxx:xxxx:60c0%enp4s0 (fe80::xxxx:xxxx:xxxx:60c0%enp4s0) 56 data bytes
64 bytes from fe80::xxxx:xxxx:xxxx:60c0%enp4s0: icmp_seq=1 ttl=64 time=0.349 ms
64 bytes from fe80::xxxx:xxxx:xxxx:60c0%enp4s0: icmp_seq=2 ttl=64 time=0.477 ms
64 bytes from fe80::xxxx:xxxx:xxxx:60c0%enp4s0: icmp_seq=3 ttl=64 time=0.479 ms

--- fe80::xxxx:xxxx:xxxx:60c0%enp4s0 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2042ms
rtt min/avg/max/mdev = 0.349/0.435/0.479/0.060 ms

But when I disable the wired network and enable the wireless network it seems that everything works correctly:

# ping -c 3 google.com
PING google.com (2a00:1450:4003:802::200e) 56 data bytes
64 bytes from mad07s09-in-x0e.1e100.net (2a00:1450:4003:802::200e): icmp_seq=1 ttl=118 time=22.2 ms
64 bytes from mad07s09-in-x0e.1e100.net (2a00:1450:4003:802::200e): icmp_seq=2 ttl=118 time=12.1 ms
64 bytes from mad07s09-in-x0e.1e100.net (2a00:1450:4003:802::200e): icmp_seq=3 ttl=118 time=14.9 ms

--- google.com ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2002ms
rtt min/avg/max/mdev = 12.118/16.394/22.199/4.255 ms
# tracepath google.com
 1?: [LOCALHOST]                        0.020ms pmtu 1500
 1:  2a02-xxxx-xxxx-xxxx-0000-0000-0000-0001.red-xxxx-xxx.customerbaf.ipv6.rima-tde.net   9.978ms 
 1:  2a02-xxxx-xxxx-xxxx-0000-0000-0000-0001.red-xxxx-xxx.customerbaf.ipv6.rima-tde.net   9.238ms 
 2:  2a02-xxxx-xxxx-xxxx-0000-0000-0000-0001.red-xxxx-xxx.customerbaf.ipv6.rima-tde.net   2.320ms pmtu 1492
 2:  2a02-xxxx-xxxx-xxxx-xxxx-xxxx-xxxx-0136.red-xxxx-xx.customer.ipv6.rima-tde.net   3.033ms 
 3:  2a02-xxxx-xxxx-xxxx-xxxx-xxxx-xxxx-0130.red-xxxx-xx.customer.ipv6.rima-tde.net  11.313ms asymm  8 
 4:  no reply
 5:  2001:1498:1:81d::b9                                  12.573ms !A
     Resume: pmtu 1492

The default route is the same, with different metric:

# ip -6 route show
[...]
default via fe80::xxxx:xxxx:xxxx:60c0 dev wlp3s0 proto ra metric 600 pref medium

Last edited by opotonil (2025-05-17 17:23:56)

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#2 2025-05-17 18:08:18

-thc
Member
Registered: 2017-03-15
Posts: 995

Re: IPv6 fail on wired network and work on wireless network

Check in both scenarios the IPv6 addresses of the adapters:

ip a

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#3 2025-05-17 18:32:35

opotonil
Member
Registered: 2009-09-12
Posts: 45

Re: IPv6 fail on wired network and work on wireless network

Wired network enabled - Wireless network disabled:

$ ip addr show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host noprefixroute 
       valid_lft forever preferred_lft forever
2: enp4s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether xx:xx:xx:xx:xx:xx brd ff:ff:ff:ff:ff:ff
    altname enxf4xxxxxxxxxx
    inet 192.168.1.237/24 brd 192.168.1.255 scope global dynamic noprefixroute enp4s0
       valid_lft 42536sec preferred_lft 42536sec
    inet6 fd70:xxxx:xxxx::8c6/128 scope global dynamic noprefixroute 
       valid_lft 42799sec preferred_lft 42799sec
    inet6 2a02:xxxx:xxxx:xxxx::8c6/128 scope global dynamic noprefixroute 
       valid_lft 42799sec preferred_lft 42799sec
    inet6 2a02:xxxx:xxxx:xxxx:f404:dd77:64d3:86e4/64 scope global dynamic noprefixroute 
       valid_lft 49162sec preferred_lft 49162sec
    inet6 fd70:xxxx:xxxx:0:758c:3d88:dae1:c379/64 scope global noprefixroute 
       valid_lft forever preferred_lft 604479sec
    inet6 fe80::xxxx:xxxx:xxxx:2d0a/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever
3: wlp3s0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether xx:xx:xx:xx:xx:xx brd ff:ff:ff:ff:ff:ff permaddr xx:xx:xx:xx:xx:xx
    altname wlxb0xxxxxxxxxx
$ ping -c 3 google.com
PING google.com (2a00:1450:4003:802::200e) 56 data bytes

--- google.com ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 2040ms

Wired network disabled - Wireless network enabled:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host noprefixroute 
       valid_lft forever preferred_lft forever
2: enp4s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether xx:xx:xx:xx:xx:xx brd ff:ff:ff:ff:ff:ff
    altname enxf4xxxxxxxxxx
3: wlp3s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether xx:xx:xx:xx:xx:xx brd ff:ff:ff:ff:ff:ff
    altname wlxb0xxxxxxxxxx
    inet 192.168.1.209/24 brd 192.168.1.255 scope global dynamic noprefixroute wlp3s0
       valid_lft 43189sec preferred_lft 43189sec
    inet6 fd70:xxxx:xxxx::e71/128 scope global dynamic noprefixroute 
       valid_lft 43192sec preferred_lft 43192sec
    inet6 2a02:xxxx:xxxx:xxxx::e71/128 scope global dynamic noprefixroute 
       valid_lft 43191sec preferred_lft 43191sec
    inet6 2a02:xxxx:xxxx:xxxx:2257:9861:f2d6:5a5f/64 scope global dynamic noprefixroute 
       valid_lft 48821sec preferred_lft 48821sec
    inet6 fd70:xxxx:xxxx:0:e583:f65:703c:e249/64 scope global noprefixroute 
       valid_lft forever preferred_lft 604791sec
    inet6 fe80::xxxx:xxxx:xxxx:65a5/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever
$ ping -c 3 google.com
PING google.com (2a00:1450:4003:802::200e) 56 data bytes
64 bytes from mad07s09-in-x0e.1e100.net (2a00:1450:4003:802::200e): icmp_seq=1 ttl=118 time=10.7 ms
64 bytes from mad07s09-in-x0e.1e100.net (2a00:1450:4003:802::200e): icmp_seq=2 ttl=118 time=12.2 ms
64 bytes from mad07s09-in-x0e.1e100.net (2a00:1450:4003:802::200e): icmp_seq=3 ttl=118 time=11.7 ms

--- google.com ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2003ms
rtt min/avg/max/mdev = 10.736/11.548/12.222/0.614 ms

Last edited by opotonil (2025-05-17 18:34:52)

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#4 2025-05-18 05:52:07

-thc
Member
Registered: 2017-03-15
Posts: 995

Re: IPv6 fail on wired network and work on wireless network

Your devices obtain two IPV6 ULA (fdXX::) and two IPV6 globally routable (2XXX::) addresses with different masks.
That's not how it's supposed to be. What device (router, DHCPv6 server) does this?

Last edited by -thc (2025-05-18 05:52:26)

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#5 2025-05-18 07:20:39

seth
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From: Don't DM me only for attention
Registered: 2012-09-03
Posts: 69,051

Re: IPv6 fail on wired network and work on wireless network

Please post the output of

find /etc/systemd -type l -exec test -f {} \; -print | awk -F'/' '{ printf ("%-40s | %s\n", $(NF-0), $(NF-1)) }' | sort -f
sudo nmap --script broadcast-dhcp-discover

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#6 2025-05-18 08:54:52

opotonil
Member
Registered: 2009-09-12
Posts: 45

Re: IPv6 fail on wired network and work on wireless network

-thc, the router is a Turris Omnia with OpenWRT 24.10.1 so I think the DHCPv6 server is odhcpd.

seth, this is the output:

$ find /etc/systemd -type l -exec test -f {} \; -print | awk -F'/' '{ printf ("%-40s | %s\n", $(NF-0), $(NF-1)) }' | sort -f
bluetooth.service                        | bluetooth.target.wants
dbus-org.bluez.service                   | system
dbus-org.freedesktop.nm-dispatcher.service | system
dbus-org.freedesktop.oom1.service        | system
dbus-org.freedesktop.resolve1.service    | system
dbus-org.freedesktop.timesync1.service   | system
display-manager.service                  | system
fstrim.timer                             | timers.target.wants
getty@tty1.service                       | getty.target.wants
gnome-keyring-daemon.socket              | sockets.target.wants
NetworkManager-wait-online.service       | network-online.target.wants
NetworkManager.service                   | multi-user.target.wants
nvidia-hibernate.service                 | systemd-hibernate.service.wants
nvidia-resume.service                    | systemd-hibernate.service.wants
nvidia-resume.service                    | systemd-suspend.service.wants
nvidia-suspend.service                   | systemd-suspend.service.wants
p11-kit-server.socket                    | sockets.target.wants
pipewire-pulse.socket                    | sockets.target.wants
pipewire-session-manager.service         | user
pipewire.socket                          | sockets.target.wants
remote-fs.target                         | multi-user.target.wants
switcheroo-control.service               | graphical.target.wants
systemd-boot-update.service              | sysinit.target.wants
systemd-oomd.service                     | multi-user.target.wants
systemd-resolved.service                 | sysinit.target.wants
systemd-timesyncd.service                | sysinit.target.wants
systemd-userdbd.socket                   | sockets.target.wants
wireplumber.service                      | pipewire.service.wants
xdg-user-dirs-update.service             | default.target.wants
# nmap --script broadcast-dhcp-discover
Starting Nmap 7.95 ( https://nmap.org ) at 2025-05-18 10:49 CEST
Pre-scan script results:
| broadcast-dhcp-discover: 
|   Response 1 of 1: 
|     Interface: enp4s0
|     IP Offered: 192.168.1.100
|     DHCP Message Type: DHCPOFFER
|     Server Identifier: 192.168.1.1
|     IP Address Lease Time: 12h00m00s
|     Renewal Time Value: 6h00m00s
|     Rebinding Time Value: 10h30m00s
|     Subnet Mask: 255.255.255.0
|     Broadcast Address: 192.168.1.255
|     Router: 192.168.1.1
|     Domain Name Server: 192.168.1.1
|_    Domain Name: lan
WARNING: No targets were specified, so 0 hosts scanned.
Nmap done: 0 IP addresses (0 hosts up) scanned in 10.14 seconds

Last edited by opotonil (2025-05-18 08:55:37)

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#7 2025-05-18 09:20:42

-thc
Member
Registered: 2017-03-15
Posts: 995

Re: IPv6 fail on wired network and work on wireless network

opotonil wrote:

-thc, the router is a Turris Omnia with OpenWRT 24.10.1 so I think the DHCPv6 server is odhcpd.

In this case double-check the IPv6 configuration on the router.

Since IPv6 offers seven different types of configuration and only some of them make sense in certain ISP scenarios (static/dynamic prefix) start with the simplest of them: SLAAC only.

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#8 2025-05-18 09:41:37

opotonil
Member
Registered: 2009-09-12
Posts: 45

Re: IPv6 fail on wired network and work on wireless network

-thc wrote:
opotonil wrote:

-thc, the router is a Turris Omnia with OpenWRT 24.10.1 so I think the DHCPv6 server is odhcpd.

In this case double-check the IPv6 configuration on the router.

Since IPv6 offers seven different types of configuration and only some of them make sense in certain ISP scenarios (static/dynamic prefix) start with the simplest of them: SLAAC only.

Default config seems SLAAC and DHCPv6 (https://openwrt.org/docs/guide-user/net … and_dhcpv6) after change to SLAAC only (https://openwrt.org/docs/guide-user/net … slaac_only) seems to work, I only get one global address and one local address.

I will try to backup and reinstall OpenWRT with default config and change only the basic to get connectivity (WAN VLAN and PPPOE)

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#9 2025-05-18 10:25:48

-thc
Member
Registered: 2017-03-15
Posts: 995

Re: IPv6 fail on wired network and work on wireless network

I can understand OpenWRTs choice of "stateful DHCPv6 with SLAAC" as a kind of "catch-all" configuration for every kind of IPv6 client.

On the other hand your Arch network management (NM) seems to get confused by that.

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#10 2025-05-18 17:09:09

opotonil
Member
Registered: 2009-09-12
Posts: 45

Re: IPv6 fail on wired network and work on wireless network

I have found the real culprit, IGMP Snooping enabled on the LAN bridge. So, DHCPv6 uses multicast?

I should have been suspicious of it, whenever I enable it and something uses multicast I have problems. I don't know if I'm doing something wrong or if there's a problem in OpenWRT or if it's a Linux problem.

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#11 2025-05-18 17:46:07

-thc
Member
Registered: 2017-03-15
Posts: 995

Re: IPv6 fail on wired network and work on wireless network

Yep - DHCP-Solicitation via multicast address ff02::1:2.

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