Case 1:Normal RRC Connection Reconfiguration Failure will lead to RRC Connection Re-establishment.Means In LTE RRC Connection Reconfiguration will be used To Setup/Release Measurements,To Setup/Modify/Release of Bearers.
In this case the RRC Connection Reconfiguration is sent to the UE by Including any of the Configuration mentioned above, But my UE is unable to comply with the configuration which is sent by eNB then UE will send RRC Connection Reconfiguration Failure then Immediately UE will do RRC Connection Re-establishment Procedure.
Case 2:RRC Connection Reconfiguration Failure while making HANDOVER Leads to RRC Connection Re-establishment.Means while Making Handover after Reserving Resources at T-eNB, SeNB will send RRC Connection Reconfiguration with Mobility Control Info(Target Cell PCI,Dedicated RACH Preamble Info,T-eNB security Info) to the UE.Then UE will access the Target Cell by using the information in RRC Connection Reconfiguration message,but UE is unable to access the Target cell because of RACH Failure then UE will send the RRC Connection Reconfiguration Failure Message then Immediately UE will do the RRC Connection Re-establishment.