IP v4 地址的范围是 0.0.0.0 到 255.255.255.255。其中,0.0.0.0 是一个特殊地址,表示所有本机的 interfaces,255.255.255.255 是一个特殊地址,表示所有本机的 interfaces 和所有 other interfaces on the network。
IP v4 地址被分为 5 个 classes:A、B、C、D 和 E。每个 class 有不同数量的 network bits 和 host bits,从而具有不同的 network 和 host 范围。
Class A: network bits = 1, host bits = 7, network range = 1-126, host range = 0-255
Class B: network bits = 2, host bits = 6, network range = 128-191, host range = 0-255
Class C: network bits = 3, host bits = 5, network range = 192-223, host range = 0-255
Class D: network bits = 4, host bits = 4, network range = 224-239, host range = 0-255
Class E: network bits = 5, host bits = 3, network range = 240-255, host range = 0-255
Class D 和 Class E 用于 special purposes,如 multicasting 和 experimental use。Class A、B 和 C 用于 general use。
例如,两个 Class C networks 192.168.1.0/24 和 192.168.1.128/24 可以 supernetted into one network 192.168.1.0/23。这个 network 有 510 host addresses (2^9 2)。
IP v4 地址的 private addressing 是将一个 network 与 the public Internet 隔离的 process。private addressing 通过使用 a private network address range 和 a public network address range,并使用 a network address translation (NAT) device 来将 private addresses 转换成 public addresses。
IP v4 地址的 public addressing 是将 a network 与 the public Internet 连接的 process。public addressing 通过使用 a public network address range。
public network address ranges 为:
0.0.0.0/0 to 10.0.0.0/8
127.0.0.0/8 to 172.16.0.0/12
172.16.0.0/12 to 192.0.0.0/8
192.0.0.0/8 to 192.168.0.0/16
192.168.0.0/16 to 223.255.255.255
224.0.0.0/4 to 239.255.255.255
IP v4 地址的 host address 不能是 all 0s or all 1s。all 0s host address 用于 the network itself,all 1s host address 用于 the broadcast address.
IP v4 地址的 network address 不能 be 0.0.0.0 or 255.255.255.255.0.0.0.0 is a special address that represents all interfaces on the local host, and 255.255.255.255 is a special address that represents all interfaces on the network.