redback lac mikrotik lns

i have a redback lac with a tunnel id and a secret. I am trying to use a mikrotik router as the lns to terminate the tunnel and then the users. I Can connect to the tunnel with a windows machine but the redback i never see in the logs. i have done packet sniffs on my eth (nortel) router interface and see the redback trying. but i never see anything in the mikrotik logs.

any ideas?

it seems it dosent understand the secret. the redback lac without the secret will pass the users on to the mikrotik with no problems.