ZBFW stands for Zone-Based Firewall, which is a feature that allows unidirectional application of IOS firewall policies between groups of interfaces known as zones. Interfaces are assigned to zones, and firewall rules are applied to specific types of traffic moving in one direction between the zones. ZBFW enforces a secure inter-zone policy by default, meaning traffic cannot pass between security zones until an explicit policy allowing that traffic is defined. The zone itself is an abstraction of multiple interfaces with the same or similar security requirements that can be logically grouped together. ZBFW is CBAC’s replacement and offers intuitive policies for multiple-interface routers, increased granularity of firewall policy application, and a default deny-all policy that prohibits traffic between firewall security zones until an explicit policy is applied to allow desirable traffic. ZBFW is supported on IOS devices running 12.4(6)T or later, and ASR devices running 12.2(33) or later. References:
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