radiusd.log not showing authentication requests

[Stefano Zanmarchi]

Hello,
I'm setting up a new radius server, copying the configuration from the
actual one (both are 2.1.12).
Everything is working in debug mode, but if I start the new radius normally
it just shows start|stop info ("ready to process requests") in the
radiusd.log file, not the authentication requests.
The actual server instead is logging fine:

Tue Jun 23 17:40:23 2015 : Auth: Login OK: [marie.curie at studenti.unipd.it]
(from client server2.unipd.it port 1 cli 00-26-b6-f8-6f-e5 via TLS tunnel)
Tue Jun 23 17:40:23 2015 : Auth: Login OK: [marie.curie at studenti.unipd.it]
(from client server2.unipd.it port 1 cli 00-26-b6-f8-6f-e5)

The "log" section of the radiusd.conf on both servers is:

log {
        destination = files
        file = ${logdir}/radius.log
        syslog_facility = daemon
        stripped_names = no
        auth = yes
        auth_badpass = no
        auth_goodpass = no
}

Is there some other setting to activate authentication logging in
radiusd.log file?
I'm sure I'm missing something, but I can't see where.

Thank you very much for your help,
Stefano