How to take an ETHB as a uplink board?
ETHB boards can be used as a uplink board after changing some key parameters
1. MA5680T(config)#undo isolate board Frame/Slot
2. MA5680T(config-if-eth-F/S)#network-role uplink
MA5600T system takes isolating all the packets broadcast in one vlan as a default configuration, so without the above settings, the packets can not be transferred to the ETHB board but discarded.