(In the experimental environment, the eth0 interface of the ASA firewall is defined as the outside area, with Security-Level: 0, connected to RouterF0/0; the eth1 interface of the ASA firewall is defined as the insdie area, with Security-Level: 100, connected to the upstream interface of the Switch; the Eth2 interface of the ASA firewall is defined as DMZ area, Security-Level: 60, connected to MailServer.
Honghu Forum_Cisco_ASA_5500 Basic Configuration.pdf)