radtest and Message-Authenticator

[Norbert Wegener]

When I send
radtest 000000000009  000000000009 brm 1812 secret xx 10.10.20.138
to a freeradiusserver, I get an access accept.
Sending the same radtest command line to an IAS, that should proxy that 
request to a freeradiusserver,
the IAS complains about a missing Message-Authenticator.
What do I have to do to get a Message-Authenticator in such a radtest 
request?
Thanks
Norbert Wegener