The value of tmnxMobProfRadAuthProbeInt specifies the interval at
which the system sends authentication probe messages to an
authentication server. An authentication probe is a 'fake'
Access-Request message for a certain username and password. If the
server responds to the Access-Request (even with an Access-
Reject), the server will be considered operational.
Note that the authentication probe messages will not be sent to
the servers that are used for accounting only.