"ip a" reports a normal situations in any case. At least, I could not see any oddities at this level, nor had I to change anything concerning just the ip addresses of my interfaces. The only interface I configured, only with NM, is eno1 with a static address:
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: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether c8:5a:cf:0f:ca:f0 brd ff:ff:ff:ff:ff:ff
altname enp0s31f6
inet 192.168.0.77/23 brd 192.168.1.255 scope global noprefixroute eno1
valid_lft forever preferred_lft forever
inet 169.254.30.62/16 brd 169.254.255.255 scope global noprefixroute eno1
valid_lft forever preferred_lft forever
3: lxcbr0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000
link/ether 00:16:3e:00:00:00 brd ff:ff:ff:ff:ff:ff
inet 10.0.3.1/24 brd 10.0.3.255 scope global lxcbr0
valid_lft forever preferred_lft forever
4: lxdbr0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
link/ether 00:16:3e:8d:ce:69 brd ff:ff:ff:ff:ff:ff
inet 10.116.239.1/24 scope global lxdbr0
valid_lft forever preferred_lft forever
inet 169.254.189.225/16 brd 169.254.255.255 scope global noprefixroute lxdbr0
valid_lft forever preferred_lft forever
inet6 fd42:a242:50fe:49d7::1/64 scope global
valid_lft forever preferred_lft forever
inet6 fe80::c83f:ad2d:1a3d:75a4/64 scope link
valid_lft forever preferred_lft forever
6: veth1bd75455@if5: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master lxdbr0 state UP group default qlen 1000
link/ether 92:5f:b6:50:48:df brd ff:ff:ff:ff:ff:ff link-netnsid 0
inet 169.254.156.137/16 brd 169.254.255.255 scope global noprefixroute veth1bd75455
valid_lft forever preferred_lft forever
As you can see there are several bridge because I have LXD on my machine, but they have been there for months.
I just have to delete the wrong default route and add the good one as I wrote in the original message. Here the "ip r" currently working (I can access the internet without problems):
As you can see, the only difference is the default route.
Here are only the syslog lines containing NetworkManager and the time of the reboot. I also removed hostname to shorten the text a bit.
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.8892] NetworkManager (version 1.30.0) is starting... (for the first time)
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.8892] Read config: /etc/NetworkManager/NetworkManager.conf (lib: no-mac-addr-change.conf)
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.8906] bus-manager: acquired D-Bus service "org.freedesktop.NetworkManager"
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.8961] manager[0x55ddfe00e010]: monitoring kernel firmware directory '/lib/firmware'.
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.8961] monitoring ifupdown state file '/run/network/ifstate'.
Apr 29 09:19:06 dbus-daemon[712]: [system] Activating via systemd: service name='org.freedesktop.hostname1' unit='dbus-org.freedesktop.hostname1.service' requested by ':1.5' (uid=0 pid=713 comm="/usr/sbin/NetworkManager --no-daemon ")
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.9479] hostname: hostname: using hostnamed
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.9479] hostname: hostname changed from (none) to "PC-GIULIANO.BNCRM.ROMA"
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.9481] dns-mgr[0x55ddfe003170]: init: dns=default,systemd-resolved rc-manager=resolvconf (auto)
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.9482] manager[0x55ddfe00e010]: rfkill: Wi-Fi hardware radio set enabled
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.9482] manager[0x55ddfe00e010]: rfkill: WWAN hardware radio set enabled
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.9528] Loaded device plugin: NMAtmManager (/usr/lib/x86_64-linux-gnu/NetworkManager/1.30.0/libnm-device-plugin-adsl.so)
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.9550] Loaded device plugin: NMWwanFactory (/usr/lib/x86_64-linux-gnu/NetworkManager/1.30.0/libnm-device-plugin-wwan.so)
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.9564] Loaded device plugin: NMWifiFactory (/usr/lib/x86_64-linux-gnu/NetworkManager/1.30.0/libnm-device-plugin-wifi.so)
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.9590] Loaded device plugin: NMBluezManager (/usr/lib/x86_64-linux-gnu/NetworkManager/1.30.0/libnm-device-plugin-bluetooth.so)
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.9608] Loaded device plugin: NMTeamFactory (/usr/lib/x86_64-linux-gnu/NetworkManager/1.30.0/libnm-device-plugin-team.so)
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.9609] manager: rfkill: Wi-Fi enabled by radio killswitch; enabled by state file
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.9609] manager: rfkill: WWAN enabled by radio killswitch; enabled by state file
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.9610] manager: Networking is enabled by state file
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.9610] dhcp-init: Using DHCP client 'internal'
Apr 29 09:19:06 dbus-daemon[712]: [system] Activating via systemd: service name='org.freedesktop.nm_dispatcher' unit='dbus-org.freedesktop.nm-dispatcher.service' requested by ':1.5' (uid=0 pid=713 comm="/usr/sbin/NetworkManager --no-daemon ")
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.9621] settings: Loaded settings plugin: ifupdown ("/usr/lib/x86_64-linux-gnu/NetworkManager/1.30.0/libnm-settings-plugin-ifupdown.so")
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.9621] settings: Loaded settings plugin: keyfile (internal)
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.9621] ifupdown: management mode: unmanaged
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.9621] ifupdown: interface-parser: parsing file /etc/network/interfaces
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.9621] ifupdown: interface-parser: source line includes interfaces file(s) /etc/network/interfaces.d/*
Apr 29 09:19:06 NetworkManager[713]: <warn> [1651216746.9622] ifupdown: interfaces file /etc/network/interfaces.d/* doesn't exist
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.9622] ifupdown: interface-parser: finished parsing file /etc/network/interfaces
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.9648] device (lo): carrier: link connected
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.9649] manager: (lo): new Generic device (/org/freedesktop/NetworkManager/Devices/1)
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.9653] manager: (eno1): new Ethernet device (/org/freedesktop/NetworkManager/Devices/2)
Apr 29 09:19:06 NetworkManager[713]: <info> [1651216746.9657] device (eno1): state change: unmanaged -> unavailable (reason 'managed', sys-iface-state: 'external')
Apr 29 09:19:07 NetworkManager[713]: <info> [1651216747.1663] modem-manager: ModemManager available
Apr 29 09:19:07 NetworkManager[713]: <info> [1651216747.2059] manager: (lxcbr0): new Bridge device (/org/freedesktop/NetworkManager/Devices/3)
Apr 29 09:19:07 NetworkManager[713]: <info> [1651216747.2106] device (lxcbr0): state change: unmanaged -> unavailable (reason 'connection-assumed', sys-iface-state: 'external')
Apr 29 09:19:07 NetworkManager[713]: <info> [1651216747.2129] device (lxcbr0): state change: unavailable -> disconnected (reason 'connection-assumed', sys-iface-state: 'external')
Apr 29 09:19:07 NetworkManager[713]: <info> [1651216747.2134] device (lxcbr0): Activation: starting connection 'lxcbr0' (510e3c5f-3673-4fa5-8aad-f45fd6797f95)
Apr 29 09:19:07 NetworkManager[713]: <info> [1651216747.2137] device (lxcbr0): state change: disconnected -> prepare (reason 'none', sys-iface-state: 'external')
Apr 29 09:19:07 NetworkManager[713]: <info> [1651216747.2139] device (lxcbr0): state change: prepare -> config (reason 'none', sys-iface-state: 'external')
Apr 29 09:19:07 NetworkManager[713]: <info> [1651216747.2141] device (lxcbr0): state change: config -> ip-config (reason 'none', sys-iface-state: 'external')
Apr 29 09:19:07 NetworkManager[713]: <info> [1651216747.2142] device (lxcbr0): state change: ip-config -> ip-check (reason 'none', sys-iface-state: 'external')
Apr 29 09:19:07 NetworkManager[713]: <info> [1651216747.2153] device (lxcbr0): state change: ip-check -> secondaries (reason 'none', sys-iface-state: 'external')
Apr 29 09:19:07 NetworkManager[713]: <info> [1651216747.2154] device (lxcbr0): state change: secondaries -> activated (reason 'none', sys-iface-state: 'external')
Apr 29 09:19:07 NetworkManager[713]: <info> [1651216747.2157] manager: NetworkManager state is now CONNECTED_LOCAL
Apr 29 09:19:07 NetworkManager[713]: <info> [1651216747.2162] device (lxcbr0): Activation: successful, device activated.
Apr 29 09:19:10 NetworkManager[713]: <info> [1651216750.0839] device (eno1): carrier: link connected
Apr 29 09:19:10 NetworkManager[713]: <info> [1651216750.0840] device (eno1): state change: unavailable -> disconnected (reason 'carrier-changed', sys-iface-state: 'managed')
Apr 29 09:19:10 NetworkManager[713]: <info> [1651216750.0846] policy: auto-activating connection 'Wired connection 1' (a697befe-510f-4687-9113-8bdbf2b83cf1)
Apr 29 09:19:10 NetworkManager[713]: <info> [1651216750.0848] device (eno1): Activation: starting connection 'Wired connection 1' (a697befe-510f-4687-9113-8bdbf2b83cf1)
Apr 29 09:19:10 NetworkManager[713]: <info> [1651216750.0849] device (eno1): state change: disconnected -> prepare (reason 'none', sys-iface-state: 'managed')
Apr 29 09:19:10 NetworkManager[713]: <info> [1651216750.0851] manager: NetworkManager state is now CONNECTING
Apr 29 09:19:10 NetworkManager[713]: <info> [1651216750.0852] device (eno1): state change: prepare -> config (reason 'none', sys-iface-state: 'managed')
Apr 29 09:19:10 NetworkManager[713]: <info> [1651216750.0855] device (eno1): state change: config -> ip-config (reason 'none', sys-iface-state: 'managed')
Apr 29 09:19:10 NetworkManager[713]: <info> [1651216750.0864] device (eno1): state change: ip-config -> ip-check (reason 'none', sys-iface-state: 'managed')
Apr 29 09:19:10 NetworkManager[713]: <info> [1651216750.0875] device (eno1): state change: ip-check -> secondaries (reason 'none', sys-iface-state: 'managed')
Apr 29 09:19:10 NetworkManager[713]: <info> [1651216750.0876] device (eno1): state change: secondaries -> activated (reason 'none', sys-iface-state: 'managed')
Apr 29 09:19:10 NetworkManager[713]: <info> [1651216750.0877] manager: NetworkManager state is now CONNECTED_LOCAL
Apr 29 09:19:10 NetworkManager[713]: <info> [1651216750.0882] manager: NetworkManager state is now CONNECTED_SITE
Apr 29 09:19:10 NetworkManager[713]: <info> [1651216750.0882] policy: set 'Wired connection 1' (eno1) as default for IPv4 routing and DNS
Apr 29 09:19:10 NetworkManager[713]: <info> [1651216750.0884] dns-mgr: Writing DNS information to /sbin/resolvconf
Apr 29 09:19:10 dbus-daemon[712]: [system] Activating via systemd: service name='org.freedesktop.resolve1' unit='dbus-org.freedesktop.resolve1.service' requested by ':1.5' (uid=0 pid=713 comm="/usr/sbin/NetworkManager --no-daemon ")
Apr 29 09:19:10 NetworkManager[713]: <info> [1651216750.0998] device (eno1): Activation: successful, device activated.
Apr 29 09:19:10 NetworkManager[713]: <info> [1651216750.1001] manager: NetworkManager state is now CONNECTED_GLOBAL
Apr 29 09:19:10 NetworkManager[713]: <info> [1651216750.1004] manager: startup complete
Apr 29 09:19:12 NetworkManager[713]: <info> [1651216752.8458] manager: (lxdbr0): new Bridge device (/org/freedesktop/NetworkManager/Devices/4)
Apr 29 09:19:12 NetworkManager[713]: <info> [1651216752.8734] device (lxdbr0): state change: unmanaged -> unavailable (reason 'connection-assumed', sys-iface-state: 'external')
Apr 29 09:19:12 NetworkManager[713]: <info> [1651216752.8746] device (lxdbr0): state change: unavailable -> disconnected (reason 'connection-assumed', sys-iface-state: 'external')
Apr 29 09:19:12 NetworkManager[713]: <info> [1651216752.8750] device (lxdbr0): Activation: starting connection 'lxdbr0' (9d799cd9-044f-48ad-8544-201f9573fd23)
Apr 29 09:19:12 NetworkManager[713]: <info> [1651216752.8751] device (lxdbr0): state change: disconnected -> prepare (reason 'none', sys-iface-state: 'external')
Apr 29 09:19:12 NetworkManager[713]: <info> [1651216752.8753] device (lxdbr0): state change: prepare -> config (reason 'none', sys-iface-state: 'external')
Apr 29 09:19:12 NetworkManager[713]: <info> [1651216752.8767] device (lxdbr0): state change: config -> ip-config (reason 'none', sys-iface-state: 'external')
Apr 29 09:19:12 NetworkManager[713]: <info> [1651216752.8768] device (lxdbr0): state change: ip-config -> ip-check (reason 'none', sys-iface-state: 'external')
Apr 29 09:19:12 NetworkManager[713]: <info> [1651216752.8777] device (lxdbr0): state change: ip-check -> secondaries (reason 'none', sys-iface-state: 'external')
Apr 29 09:19:12 NetworkManager[713]: <info> [1651216752.8778] device (lxdbr0): state change: secondaries -> activated (reason 'none', sys-iface-state: 'external')
Apr 29 09:19:12 NetworkManager[713]: <info> [1651216752.8782] device (lxdbr0): Activation: successful, device activated.
Apr 29 09:19:13 NetworkManager[713]: <info> [1651216753.6171] manager: (vethdeccbe5b): new Veth device (/org/freedesktop/NetworkManager/Devices/5)
Apr 29 09:19:13 NetworkManager[713]: <info> [1651216753.6176] manager: (veth1bd75455): new Veth device (/org/freedesktop/NetworkManager/Devices/6)
Apr 29 09:19:13 NetworkManager[713]: <info> [1651216753.6206] device (vethdeccbe5b): carrier: link connected
Apr 29 09:19:13 NetworkManager[713]: <info> [1651216753.6208] device (veth1bd75455): carrier: link connected
Apr 29 09:19:13 NetworkManager[713]: <info> [1651216753.6334] device (lxdbr0): carrier: link connected
Apr 29 09:19:13 NetworkManager[713]: <info> [1651216753.8477] device (lxdbr0): carrier: link connected
Apr 29 09:19:22 systemd[1]: NetworkManager-dispatcher.service: Succeeded.
Apr 29 09:20:57 NetworkManager[713]: <info> [1651216857.8215] agent-manager: agent[a37872fe9bb85396,:1.119/org.gnome.Shell.NetworkAgent/1271201487]: agent registered
I can definitely esclude that. I turned off my machine and nobody answer to ping to its address.
Many thanks.