Task 6.6: Configuring a Packet Filter
Packet filters are a fundamental component of every router and firewall, and are built into virtually every operating system. They primarily operate at Layer 3 of the Open Systems Interconnection (OSI) model, but have functionality at both Layer 3 and Layer 4. They are fast, easy to configure, and strong.
The downside of packet filters is that they are not very intelligent. Packet filters either allow an IP/port combination or they block the IP/port combination. They are either wired open or wired closed.
Most contemporary firewalls combine the packet filter (called a generation 1 firewall) with a proxy service (called a generation 2 firewall) and a stateful inspection engine (called a generation 3 firewall). ...
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