If it happens when trying to remove de ip address e.g
ip addr del 2a01:xxxx:xxxx:xxxx::2 dev enp35s0
try specifying the subnet mask like so
ip addr del 2a01:xxxx:xxxx:xxxx::2/64 dev enp35s0
dmesg log:
~$ sudo dmesg -H -w
...
[pro15 19:12] RTL8226B_RTL8221B 2.5Gbps PHY r8169-0-2a00:00: Downshift occurred from negotiated speed 100Mbps to actual speed 10Mbps, check cabling!
[ +0,000012] r8169 0000:2a:00.0 enp42s0: Link is Up - 10Mbps/Full (downshifted) - flow control off
[ +2,048824] r8169 0000:2a:00.0 enp42s0: Link is Down
[ +8,959020] RTL8226B_RTL8221B 2.5Gbps PHY r8169-0-2a00:00: Downshift occurred from negotiated speed 100Mbps to actual speed 10Mbps, check cabling!
[ +0,000014] r8169 0000:2a:00.0 enp42s0: Link is Up - 10Mbps/Full (downshifted) - flow control off
[ +0,163394] r8169 0000:2a:00.0 enp42s0: Link is Down
[ +1,240247] audit: type=1107 audit(1702663934.240:136): pid=1078 uid=103 auid=4294967295 ses=4294967295 subj=unconfined msg='apparmor="DENIED" operation="dbus_method_call" bus="system" path="/org/freedesktop/timedate1" interface="org.freedesktop.DBus.Properties" member="GetAll" mask="send" name=":1.113" pid=2106 label="snap.firefox.firefox" peer_pid=5540 peer_label="unconfined"
exe="/usr/bin/dbus-daemon" sauid=103 hostname=? addr=? terminal=?'
[ +7,588296] RTL8226B_RTL8221B 2.5Gbps PHY r8169-0-2a00:00: Downshift occurred from negotiated speed 100Mbps to actual speed 10Mbps, check cabling!
[ +0,000013] r8169 0000:2a:00.0 enp42s0: Link is Up - 10Mbps/Full (downshifted) - flow control off
[ +1,259109] r8169 0000:2a:00.0 enp42s0: Link is Down
[ +8,866622] RTL8226B_RTL8221B 2.5Gbps PHY r8169-0-2a00:00: Downshift occurred from negotiated speed 100Mbps to actual speed 10Mbps, check cabling!
[ +0,000013] r8169 0000:2a:00.0 enp42s0: Link is Up - 10Mbps/Full (downshifted) - flow control off
[ +0,047328] r8169 0000:2a:00.0 enp42s0: Link is Down
[ +8,784982] RTL8226B_RTL8221B 2.5Gbps PHY r8169-0-2a00:00: Downshift occurred from negotiated speed 100Mbps to actual speed 10Mbps, check cabling!
[ +0,000012] r8169 0000:2a:00.0 enp42s0: Link is Up - 10Mbps/Full (downshifted) - flow control off
[ +0,214446] r8169 0000:2a:00.0 enp42s0: Link is Down
[ +11,364429] r8169 0000:04:00.0 enp4s0: Link is Up - 100Mbps/Full - flow control off
[ +0,000016] IPv6: ADDRCONF(NETDEV_CHANGE): enp4s0: link becomes ready
[ +0,500115] r8169 0000:04:00.0 enp4s0: Link is Down
...
Check the cabling. Plug/unplug the cables from the router and other devices. After this the problem was resolved.
Check your /etc/resolv.conf if your distro is using that. On Ubuntu systemd-resolvd manages that file, so check systemd-resolvd service.
If that seems fine, then it might a symptom of the below problem.
Happens when pinging an IP address.
Most likely an issue with a missing route.
Check with ip r and add the route.
Here's an example of missing route on a VM server with assigned IPs to the eth0 interface already.
# ip a
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
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 02:00:00:12:14:7c brd ff:ff:ff:ff:ff:ff
inet 198.50.177.218/32 brd 198.50.177.218 scope global eth0
valid_lft forever preferred_lft forever
inet6 2607:5300:203:1735:198:50:177:218/64 scope global
valid_lft forever preferred_lft forever
inet6 fe80::ff:fe12:147c/64 scope link
valid_lft forever preferred_lft forever
...
# ip r
10.0.1.0/24 dev tun1 proto kernel scope link src 10.0.1.79
169.254.0.0/16 dev eth0 scope link metric 1002
172.17.0.0/16 dev docker0 proto kernel scope link src 172.17.0.1
...
# ip -6 r
unreachable ::/96 dev lo metric 1024 error -113 pref medium
unreachable ::ffff:0.0.0.0/96 dev lo metric 1024 error -113 pref medium
...
default via 2607:5300:203:1735:: dev eth0 metric 1 pref medium
default via 2607:5300:203:1735:: dev eth0 metric 1024 pref medium
...
[root@xor1 NetworkManager]# ip r
In above output ipv4 is missing a default route, and ipv6 is ok.
To fix this case you would run:
# ip route add 66.70.179.0/24 dev eth0 src 198.50.177.218 # ip route add default via 66.70.179.53 # ping 8.8.8.8 PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data. 64 bytes from 8.8.8.8: icmp_seq=1 ttl=113 time=1.31 ms ...
You have to know the gateway IP, 66.70.179.53 above, then add a direct route to that because any gateway must be reachable directly on connected interfaces. This gateway IP is actually a bridge br0 interface on the VM host and that's serving as the interface for all of the VMs there.