The previous chapter focused on a router-based IOS Firewall solution, whereas this chapter mainly focuses on
the hardware-based, purpose-built Cisco Firewall technology.
The chapter discusses various types of Cisco Firewalls available and includes a brief overview of each model.
The chapter is divided into two segments??”features and configuration based on the following:
Firewall appliance software for PIX 500 and ASA 5500 platforms
Firewall module software for Firewall Services Module (FWSM)
The chapter takes a closer look at core concepts, such as firewall modes, security contexts, stateful inspection,
the Adaptive Security Algorithm, IP routing, various types of Network Address Translation (NAT), the control of
traffic flow and network access through the firewall, the Modular Policy Framework (MPF), and the provisioning
of high-availability and resilient networks.
Firewalls Overview
A firewall is a hardware or software solution implemented within the network to enforce security policies by
controlling network access. The traditional function of firewalls has evolved from the original function of
protecting a network from unauthorized external access. Besides protecting the perimeter of a network, today's
firewalls implement the following: access control, virtual private network (VPN) services, quality of service
(QoS) features, redundancy mechanisms, and much more.
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