My Prox Mox Server suddendly loses connectivity and cannot be reached. Neither the machines it virtualizes nor the web interface itsself is reponding.

when checking journalctl I stumbled upon the following error

e1000e 0000:00:19.0 eno1: Detected Hardware Unit Hang

Here is the proposed solution: e1000e eno1: Detected Hardware Unit Hang: | Proxmox Support Forum

Disabling TCP checksum offloading:

ethtool -K eth0 tx off rx off

Have it integrated at boot time : e1000e:reset adapter unexpectedly | Proxmox Support Forum

> cat /etc/network/interfaces

auto lo
iface lo inet loopback

iface eno1 inet manual

auto vmbr0
iface vmbr0 inet static
    address 10.1.10.10/23
    gateway 10.1.10.1
    bridge-ports eno1
    bridge-stp off
    bridge-fd 0
    post-up /sbin/ethtool -K $IFACE tso off gso off gro off rxvlan off txvlan off

OR

cat /etc/network/interfaces
auto lo
iface lo inet loopback

iface eno1 inet manual
post-up /sbin/ethtool -K $IFACE tso off gso off gro off

auto vmbr0
iface vmbr0 inet static
address 10.0.1.10/24
gateway 10.0.1.1
bridge-ports eno1
bridge-stp off
bridge-fd 0