FirewallBuilder

You are trying to execute an iptables script generated by Firewall Builder but get an error message "Interface eth0 does not exist" or similar.

There are several conditions that may cause this error.

The script generated by Firewall Builder uses the tool /sbin/ip to verify configuration of the firewall interfaces and make sure that interfaces of the real firewall machine correspond to the interface objects created in the GUI. You may get this error if the tool /sbin/ip is not installed on your system. All modern Linux distributions come with the package iproute2 which includes /sbin/ip; check if iproute2 is installed and /sbin/ip exists.

Another case when you may encounter this error is when firewall script is executed prematurely during the boot sequence and interface really does not exist at that time. For example, interface ppp0 is created only when the system is configured for PPP and the daemon pppd is running. If the firewall script is activated before the daemon started during the boot sequence, interface ppp0 is not there yet, which leads to this error. Make sure you start firewall script after all interfaces has been initialized.