图2l.1ARP(Address Resolution Protocol)操作逻辑地址到物理地址 Looking for physical address of a node with IP address 141.23.56.23 之 Request System A System B a.ARP request is broadcast The node physical address isA4:6E:F4:59:83:AB Reply System A System B b.ARP reply is unicast 21.3 21.3 图 21.1 ARP （Address Resolution Protocol）操作（逻辑地址到物理地址的转换）