20. ■ iptables
http://www.netfilter.org/projects/iptables/
iptables is the userspace command line program used to configure
the Linux 2.4.x and 2.6.x IPv4 packet filtering ruleset. It is targeted
towards system administrators.
Since Network Address Translation is also configured from the
packet filter ruleset, iptables is used for this, too.
The iptables package also includes ip6tables. ip6tables is used for
configuring the IPv6 packet filter.
IPv4 packet
filtering ruleset.
27. ■ ebtables
http://ebtables.sourceforge.net/
The ebtables program is a filtering tool for a Linux-based bridging
firewall. It enables transparent filtering of network traffic
passing through a Linux bridge. The filtering possibilities are
limited to link layer filtering and some basic filtering on higher
network layers. Advanced logging, MAC DNAT/SNAT and
brouter facilities are also included.
Link layer
filtering