authentication using radius backend

[Konrad]

Hello All,

i'm installing tacacs using a 2fa with a duo-proxy. this proxy wants a user with a password string : password,yubikey-top"

however, it should work as a radius server 

Duo Two-Factor Authentication with RADIUS and Primary Authentication | Duo Security

i already configuret a secret and a ip for the auth.

now my tacacs conf:

#!../../../sbin/tac_plus

id = spawnd {
        listen = { port = 49 }
        spawn = {
                instances min = 1
                instances max = 10
        }
        background = no
}

id = tac_plus {
        debug = PACKET AUTHEN AUTHOR

        access log = /tmp/access.log
        authorization log = /tmp/author.log
        accounting log = /tmp/acct.log


#----- mavis backend -----
        mavis module = tacinfo_cache {
                directory = /tmp/tacinfo
        }


        mavis module = external {
                exec = /usr/local/lib/mavis/mavis_tacplus_radius.pl
                setenv RADIUS_HOST = 10.250.10.62:1812
                setenv RADIUS_SECRET = "3UdkX39KaOy0sUfuDePF9DFKLUM9XxeH"
                setenv RADIUS_GROUP_ATTR = Class
                setenv RADIUS_PASSWORD_ATTR = Password
        }

        user backend = mavis
        login backend = mavis
        pap backend = mavis

#----- global settings -----
        host = world {
                address = ::/0
                prompt = "Willkommen bei meiner Projektarbeit!"
                enable 15 = clear secret
                key = [secretforswitch]
        }

#----- groups -----
        group = admin {
                service = shell {
                        default command = permit
                        set priv-lvl = 15
                        default attribute = permit
                }
        }



#----- user ------
        user = myuser {
                member = admin
        }
}

unfortunatly i cant see a incoming auth on my duo-proxy.

using the radmavis external modul is not a option since i cant locate it under /usr/local/sbin

i hope you can help me. Thank you!

Konrad