On rare occasions, due to changes in the network interface or other reasons, the firewall service may get stuck. In such cases, we can restart the service using the following command:

    # systemctl restart pve-firewall

If the previous command does not help, then check the syslog of the node to look for a clue. If nothing helps, then a reboot will clear any firewall issues. As of Proxmox VE 5.0, if a firewall becomes inactive, it does not fall back on a predefined set of protection; a firewall simply becomes nonexistent.