frequent network collapse possibly due to bridging

Hakan E. Duran ehakanduran at
Fri Jan 21 14:42:58 UTC 2022


I would like some help to troubleshoot the problem I have been having
lately with my VM host, which contains 5 VMs, one of which is for
pi-hole, unbound services. It has been a relatively common occurrence in
the last few weeks for me to find that the host machine has lost its
network when I get back home from work. Restoring the VM/VMs do not fix
the problem, the host needs to be restarted for a fix, otherwise there
is both loss of name resolution, as well as an internet connection; I
cannot ping even IPs such as Since I use the pi-hole VM as the DNS
server for my LAN, this means that my whole LAN gets disconnected from
internet, until the host machine is rebooted. The host machine has a
little complicated network setup: the two gigabit connections are bonded
and bridged to the VMs; however this set up has been serving me so well
for several years now. The problem, on the other hand, appeared a few
weeks ago. This doesn't happen every day but often enough to be annoying
and disruptive for my family.

My question is, how can I troubleshoot this problem and figure out
whether it is truly due to network bridging somehow collapsing or not? I
tried to find some log files but all I could find were the
/var/log/libvirt/qemu/$VM files, and the particular log file for the pi-hole
VM reported the following lines; however, I am not sure if they are
associated with a real crash or just due to shutting down and restarting
the host (please excuse the word-wrapping):

char device redirected to /dev/pts/2 (label charserial0)
qxl_send_events: spice-server bug: guest stopped, ignoring
2022-01-20T23:41:17.012445Z qemu-system-x86_64: terminating on signal 15 from pid 1 (/sbin/init)
2022-01-20 23:41:17.716+0000: shutting down, reason=crashed
2022-01-20 23:42:46.059+0000: starting up libvirt version: 7.10.0, qemu
version: 6.2.0, kernel: 5.10.89-1-MANJARO, hostname: -redacted-

Please excuse my ignorance but is there a way to restart the
networking without rebooting the host machine? This will not solve my
problem since I won't be able to reach to the host remotely if the
networking is down. The real solution would be preventing these network
crashes and the first step in that would be effective troubleshooting in
my opinion. Any input/guidance will be greatly appreciated.

I can provide more info about my host/VM(s) if the above is not adequate.


Hakan Duran

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