This section covers the Cisco IOS Firewall and provides sample configurations for both the IOS Classic Firewall and IOS Zone-Based Firewall.
IOS Firewall is firewall functionality that is included within specific feature licenses of the Cisco IOS. Cisco IOS is the operating system that most Cisco devices operate. All routers, including the new Integrated Services Routers (ISR) run Cisco IOS.
Cisco IOS has had a form of firewalling included since the very early releases. This was in the form of packet-filtering technology. This was the first generation of firewall technology.
Packet filtering is implemented in Cisco IOS by what Cisco calls access lists. Nearly all Cisco routers in service will have access lists configured, ...