Hosts have no idea of the physical details of their network and assume it to be a flat network in which they can reach any destination simply by sending an ARP request.

• 对于客户端来说；它们并不清楚这个网段的实际物理结构(拓扑)；它们只是把这个网段设想成只要发送ARP查询就能到达任何目的地址的平面网段.