You run out of free memory which in combination with too many network services running cause that OOM killer shuts down network in order to prevent chaos in system.
Which at the end would cause kernel panic error and unexpected system restart.
I have set a new parameter to keep always 64MB of free memory what should prevent causing this in future.
echo vm.min_free_kbytes = 65536 >> /etc/sysctl.conf
sysctl -p /etc/sysctl.conf