子网掩码由四个字节组成，它的值为255时表示IP地址中网络地址的部分，值为0时则识别IP地址中表示主机号的部分。

The subnet mask is an octet that USES the number 255 to represent the network address portion of the IP address and a zero to identify the host portion of the address.

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子网掩码是一个32位地址，用于屏蔽ip地址的一部分以区别网络地址和主机地址。

Subnet mask is a 32-bit address, IP address used to shield part of the difference between a network address and host address.

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IP地址的网络地址部分里的所有字节都被设置为0。请输入一个有效的IP地址和子网掩码组合。

All of the bits in the network address portion of the IP address are set to 0. Please enter a valid combination of IP address and subnet mask.

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