Systems and methods of setting up an E1 interface for a gNB are described, A transmitting entity of the gNB-CU-CP and gNB-CU-UP initiates the first TNL association between the gNB-CU-CP and gNB-CU-UP, and is also limited to initiating the E1 Setup procedure. The transmitting entity sends an E1 SETUP REQUEST message to set up the E1 interface. Afterwards, a message is received from the receiving entity. The transmitting entity determines that the setup of the E1 interface is successful if the message contains IEs of an E1 SETUP RESPONSE message. The types of IEs include a message type IE and a name of the transmitting entity.