pppd-pam + radiusd question

["Alex V. Toropov" <alex@ct.spb.ru>]

Hi, all
I'm trying to use dial-in ppp server with the folloing config:
mgetty monitors modem. On detecting AutoPPP fires pppd (with pam support)
pppd authorize user via radiusd throug pam_radius_auth.so get from
freeradius.org.

The problem is the following:
User authenticated only if he exists in /etc/passwd on machine, where
mgetty+pppd lives!
And his password in /etc/shadow doesn't matter. he just need to be a local
user.
Can anybody tell me why do I need to have this user?

AFAIK mgetty register a_ppp user, not user authenticating throu PAP.
Radiusd authentication succeded in any case (I'v seen success message from
pam_radius_auth
in /var/log/syslog) of user existance in local pwdb.

I have the following config for pam:
/etc/pam.d/ppp:
auth          required    pam_nologin.so
auth          sufficient   pam_radius_auth.so debug
session    required    pam_radius_auth.so

TIA Alex