it is possible in the BSS and probably possible in the NSN, but it is STRONGLY not recommended ! it yields to a serious security issue : it would then be very easy to hack of your IMSI’s. A hacker can use IMSI’s to make free calls, etc…
we are using motorola BSS which affected severely by the IOI so we want to use IMSI to reach the subscriber. Do you know which setting i need to enable to get the first attempt on IMSI directly in motorola BSS