中文摘要：

二层网络以交换机为交换设备，以MAC地址表为搜索依据，其搜索次数很大。三层网络以路由器和交换机联合作为交换设备，其中路由器以路由表为搜索依据，将广播域进行了分割，综合搜索次数大大降低，从而使大型网络的地址搜索时间减少到可接受的范围。本文通过详细的分析，比较了以交换机为主的二层网络和以路由器为主的三层网络之搜索差别。从而揭示二层网络和三层网络的本质差别。

英文摘要：

The two-layer network uses switch as switching equipment according to the MAC address table which requires a large number of searching times. The three-layer network uses router and switch together. The router splits the broadcast domain and searches the networks based on routing table, so that the total number of searching times are reduced to an acceptable range. The difference of searching times between two-layer switch-based network and three-layer router-based network is compared and their essential difference is revealed.