The AMOs SDAT, ACSU and APRT allow only numbers, that leads to a valid wabe result. Call processing, when trying to use the administered alternate routing destination number does a lot of additional plausibility checks in relation to the OOS scenario, the involved devices, the READY state of the alternate destination etc.

The main goal of this additional checks are, to avoid loops in the network and to allow other alternate destinations (call_forward), if the designed alternate routing numbers would lead to a invalid or not seizable destination.

HFA IP phones with the authorization for moving their logon from OpenScape 4000 to OpenScape Business/HiPath 3000 may be registered already in OpenScape 4000 and not yet deregidtered in OpenScape Business/HiPath 3000. In order to avoid an alternate routing loop between this 2 locations, the IP address of the partner gateway has to be administered for the related source group (of the HFA IP phones).

Call processing, when finding out, that the calling device transports the same IP address as administered in the source group of the called HFA IP phone, avoids an alternate routing.