Implement Hostname Validation in Local Mode {#ttp-sis-ad-app-implement-hostname-validate-intro}
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When operating in Local mode, your app can optionally perform hostname validation for enhanced security. When the Android device is activated, a certificate is generated on the device. The certificate includes a Subject Alternative Name (SAN). This SAN appears as a Domain Name System (DNS) entry for the Acceptance Devices app server.  
This is the SAN format: `{terminal-serial-number}.cybs.seclib.io`.  
To enable hostname validation or connect to the Android device using the SAN instead of its IP address, update your system's `hosts` file to include both the terminal's IP address and its corresponding SAN.