ASA DMZ, INSIDE, and OUTSIDE Interface Security Levels

An ASA device will assign security levels to specific interfaces. By default, when the command nameif INSIDE is used to identify an interface, it is assigned a security level of 100. The command nameif OUTSIDE as well as all other names assigned to an interface on an ASA will result in a default security level of 0. This includes the nameif DMZ command as well.

Typically, when creating a ASA DMZ interface, you must manually change the security level from 0 to some value between the INSIDE and OUTSIDE security levels.

Always check documentation of your particular setup, or test it out yourself before applying, as default behaviors may vary or be modified from version to version and platform to platform.

Links

https://networklessons.com/cisco/asa-firewall/cisco-asa-security-levels