通过指定网络标志和主机标志,IP 地址形成了一个等级结构的地址空间,便于组织和管理。但是在很多情况下,A、B、C 类地址满足不了实际需求,例如:情掘一:某公司网络申请了一个 B类地址,我们知道,一个 B 类网络可以容纳65534台主机,而该公司只有40000台主机,所以将造成25534个 IP 地址的浪费,即使该公司有65534台主机,那 By specifying network flags and host flags, IP addresses form a hierarchical address space that is easy to organize and manage. However, in many cases, A, B, and C addresses can not meet the actual requirements. For example, if a corporate network applies for a Class B address, we know that a Class B network can accommodate 65534 hosts, and that the company Only 40000 hosts, it will result in the waste of 25,534 IP addresses, even if the company has 65,534 hosts, that