Linux Firewalls, Third Edition

Configuration Options for a Larger or Less Trusted LAN

A business or an organization, and many home sites, would use more elaborate, specific mechanisms than the simple, generic forwarding firewall rules presented in the preceding two sections for a trusted home LAN. In less trusted environments, firewall machines are protected from internal users as strongly as from external users.

Port-specific firewall rules are defined for the internal interfaces as well as for the external interfaces. Internal rules might be a mirror image of the rules for the external interfaces, or the rules might be more inclusive. What is allowed through the choke firewall machine's internal network interface depends on the types of systems running on the LAN and the ...