asterisk <---IAX2---> asterisk

i have two asterisk Boxes:

mobile users<--ISDN/PRI->BOX A<--IAX2-->BOX B.

(1)CALLERID(dnid) issue
When mobile users dial DDI number assigned to BOX A, the CALLERID(dnid) is available. But when Box A forward the call to BOX B, the CALLERID(dnid) is empty within Box B dialplan.

To work around this problem, i make an agreement between Box A and Box B. When Box A dial Box B, it specifies the IAX2/peer/extensionnumber, where extension number is the CALLER(dnid) of BOX A. And in dialplan of Box B, add Set(CALLERID(dnid)=${EXTEN}) to reset the CALLERID(dnid).

(2)CALLERID(num) issue:
To send the caller ID to box B, sendani=yes, need to be configured in the box A peer configuration

(3)Native transfer
To control the media path, notransfer=yes, need to be configured in the Box B.