There are two NG-SDH network elements A and B. A is the gateway network element. The network administrator manages B through ECC routing through A. The network administrator can log in to A but cannot log in to B through A. What are the possible reasons? (Multiple choice)
A. No crossbar inserted
B. Manually set up ECC routing
C. The optical board connected to B does not create a logic board
D. The main control board is abnormal
Answer: ABD