文章内容

2019/10/12 20:05:29,作 者: 黄兵

CIDR,子网掩码和可用IP地址快速参考指南(备忘单)

快速参考子网和CIDR指南。

什么是 /28?/26 可以使用几个IP?好吧,请参见下表!

可用IP是IP总数减去网络IP和广播IP。

CIDR

子网掩码

IP总数

可用IP

/ 32255.255.255.2551个1个
/ 31255.255.255.25420
/ 30255.255.255.25242
/ 29255.255.255.24886
/ 28255.255.255.2401614
/ 27255.255.255.2243230
/ 26255.255.255.1926462
/ 25255.255.255.128128126
/ 24255.255.255.0256254
/ 23255.255.254.0512510
/ 22255.255.252.010241022
/ 21255.255.248.020482046
/ 20255.255.240.040964094
/ 19255.255.224.081928190
/ 18255.255.192.016,38416,382
/ 17255.255.128.032,76832,766
/ 16255.255.0.065,53665,534
/ 15255.254.0.0131,072131,070
/ 14255.252.0.0262,144262,142
/ 13255.248.0.0524,288524,286
/ 12255.240.0.01,048,5761,048,574
/ 11255.224.0.02,097,1522,097,150
/ 10255.192.0.04,194,3044,194,302
/ 9255.128.0.08,388,6088,388,606
/ 8255.0.0.016,777,21616,777,214
/ 7254.0.0.033,554,43233,554,430
/ 6252.0.0.067,108,86467,108,862
/ 5248.0.0.0134,217,728134,217,726
/ 4240.0.0.0268,435,456268,435,454
/ 3224.0.0.0536,870,912536,870,910
/ 2192.0.0.01,073,741,8241,073,741,822
/ 1128.0.0.02,147,483,6482,147,483,646
/ 00.0.0.04,294,967,2964,294,967,294

A类IP地址的默认子网掩码为255.0.0.0(由于255相当于二进制的8位1,所以也缩写成“/8”,表示网络号占了8位);

B类的为255.255.0.0(/16);

C类的为255.255.255.0(/24)

/30就是255.255.255.252

/32就是255.255.255.255


参考资料:CIDR, Subnet Masks, and Usable IP Addresses Quick Reference Guide (Cheat Sheet)

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