Duo Proxy, SonicWall VPN, SMS Passcode FAILURE "Invalid passcode"

[walko]

According to the DUO Authentication Logs, Duo fails almost half the time for all users.  The logs show: SMS Passcode FAILURE Invalid passcode. My question is: Why? Why does it fail nearly half the time.

We use SonicWall VPN. We use Duo Authentication Proxy and RADIUS. Duo sends users an SMS a code.

Thank you.

[DuoKristina]

By design when someone wants to use SMS passcode in a RADIUS config and they select SMS as the factor (or append ,sms to the password) the auth fails and the passcode is sent, then the user repeats the login this time specifying the passcode that was received.

The description of the sms factor in these locations mentions the initial auth fails when SMS passcode is requested.

https://duo.com/docs/sonicwallsra-alt#test-your-setup

https://guide.duo.com/auto-mode#choosing-a-different-device-or-method

[walko]

Makes sense, except for the outliers, there are some successful logins which do not fit that pattern.  But thanks. It does explain some of the logs.