当我显示一个交换机接口信息时，有line protocol和Link：

Switch-A(config-if)# show interface gigabitethernet 0/3 

Gi0/3 up, line protocol is up (connected)
Bridge Port Type: Customer Bridge Port

Hardware Address is 0c:c4:7a:fd:ca:1e 
MTU  1500 bytes, Full duplex, 1 Gbps,  No-Negotiation
HOL Block Prevention enabled.
Input flow-control is off,output flow-control is off

Link Up/Down Trap is enabled 

我想知道它们是什么？我知道一个是管理员可以关闭，另一个是物理连接。