question on challenge message

[Nagaraj Venkatapuram]

what is the configuration required on radius server(freeradius ver1.0.5) to
send challenge messages to the radius client ?
How does Radius server determine when to send challenge messages to the
client ?
 Thanks,
N
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.freeradius.org/pipermail/freeradius-users/attachments/20050928/b0dacb7d/attachment.html>