Question: What action should eNB1 take if it receives an X2 SETUP REQUEST, responds with an X2 SETUP RESPONSE, but then receives an X2 SETUP FAILURE from the peer entity on the same X2 interface?
Option 1: Reinitiate the X2 Setup procedure with a new X2 SETUP REQUEST message.
Option 2: Ignore the X2 SETUP FAILURE message and consider the X2 interface operational.
Option 3: Consider the X2 interface as non-operational and the procedure as unsuccessfully terminated.
Option 4: Send an additional X2 SETUP RESPONSE to confirm the initial response.
Explanation: If eNB1 responds with an X2 SETUP RESPONSE but then receives an X2 SETUP FAILURE, it indicates a failure in establishing the X2 interface. Thus, eNB1 should consider the X2 interface as non-operational and the setup procedure as unsuccessfully terminated to maintain network integrity and prevent potential errors or conflicts.