Cisco Secure Firewall Services Module (FWSM)

Chapter 4 Understanding Security Levels

The fundamental premise of a firewall is to enforce security policies within a network or between networks. The FWSM uses security levels as a basic principle for the differentiation of interfaces in which the security policies are applied. This chapter helps to explain the intricacies of security levels and how they can be used to enforce your specific security requirements.

Security levels are numeric values between 0 and 100, assigned to an interface, with 0 being the least secure and 100 being the most secure. These values help to define a level of trust associated to an interface, specifically in how it relates to interfaces of different values. For example, the outside interface generally has a value ...