网络工程师综合教程-第七章网络层基础及子网规划 互联网的各项应用，其实都是分层的，也就是各位网络达人常说的OSI七层模型。确定能够划分的网络数量，网络划分-Network Engineer Integrated Course- the basis of Chapter VII of the network layer and the application of the Internet subnet planning, in fact, are hierarchical, that is