A network comprising a first base station (BS) and a second BS is configured to execute instructions of the first BS connecting to a communication device via a first cell of the first BS with a signaling radio bearer (SRB); the second BS as a secondary node (SN) connecting to the communication device via a second cell while the first BS as a master node (MN) connecting to the communication device; the first BS transmitting a SN Modification Request message to a second BS to add or modify a configuration of the SN for the communication device in dual connectivity (DC); and the second BS transmitting a SN Modification Request Acknowledge message comprising to the first BS in response to the SN Modification Request message, wherein the SN Modification Request Acknowledge message comprises a new or modified configuration and a random access (RA) channel (RACH) configuration.