OSPF 设计为支持可变长度子网掩码。

OSPF was designed to support variable-length subnet masking (VLSM).

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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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对于本例来说，可以将IP地址设置为192.168.128.1，将子网掩码设置为255.255.255.0。

For this example, set the IP address to 192.168.128.1 and the subnet mask to 255.255.255.0.

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