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文件名称：子网掩码-CCNA中文版PPT
文件大小：10.75MB
文件格式：PPT
更新时间：2021-04-25 17:52:45
CCNA
子网掩码
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Emphasize: Turn on more bits to represent subnets.
Compare the default or standard subnet mask with the subnet mask in the slide.
The following are the rules for IP addressing:
An address is 32 bits, divided into three components:
First octet rule bits
Network bits (path selection bits)
Node bits
The first octet rule states that the most significant bit pattern in the first octet determines the class of the address.
Path selection bits cannot be all ones or zeros.
Certain addresses are reserved. RFC 1918 defines some of those.
Prefix or mask one bits are path selection significant; zero bits are host bits and therefore not significant.
Use the logical AND to combine the address and mask bits to get the subnet address.
The maximum number of available subnets equals 2 prefix bits - 2; the maximum number of available hosts equals 2 32- prefix bits - 2.