LTE- X2Handover

Question

Through my knowledge , In Intra X2Handover, The SeNB sends the eNB Configuration Transfer message to the MME(To get the X2 tunnel of the TeNB). but here how the MME knows about the TeNB IP?(Is it based on the Target EnodeB Id present in Configuration Message).
Does the MME maintains list of Enodeb Ids in its list.

Answer 1

eNodeB sends eNodeB configuration transfer message to MME and this message contains SON configuration transfer IE which in turn contains target eNodeB Global ID. MME gets and stores Global eNodeB Id for each eNodeB during S1-setup procedure.
Global eNodeB Id is combination of PLMN and eNodeB ID (macro/femto).

Comments

I am not sure if eNB Configuration Transfer is a mandatory procedure to be exchanged during X2 Handover. The purpose of Configuration Transfer API is primarily for RIM (RAN information Manager) procedure where MME transparently transfers the information of LTE CELL to another RAT (3G) cell.

The switching of ERABs through tunnel IP happens through Path Switch Procedure where both target and MME exchanged the DL/UL IP/TEIDs during HO for data resumption. MME needs to have an active S1 link already with target eNB.