188.12.1.0网段划分为8个子网，需要用什么子网掩码？

質問

思考

Rethinking the network class and subnetting

I need to answer in Chinese. The user's question is about subnetting and specifically the range 188.12.1.0. Since 188.x falls within Class B (128–191), the default subnet mask is /16. However, they mention dividing into 8 subnets, which suggests they might be treating this as a Class C (using /24). It’s tricky!

Deciding how to approach subnetting for 188.12.1.0

Maybe they meant the Class B network 188.12.0.0 instead of 188.12.1.0. But if they’re assuming a /24 network, we might need to borrow 3 bits (for 8 subnets), making the mask /27. Though, if it's Class B /16 and they divide into 8 subnets, it would be a /19 mask. I'll provide both with explanations to cover the ambiguity.

Thought for 18s

回答

把一个网段划成 8 个子网，需要借 3 位子网位（因为 $2^3 = 8$ ）。

但你给的 188.12.1.0 在“按类默认掩码”里属于 B 类地址（默认 /16），对应网络应写成 188.12.0.0/16；而很多题目又把“x.x.x.0”默认当作 /24 来算。两种常见理解对应的子网掩码分别是：

① 若题目默认是 /24（把 188.12.1.0 当作一个 /24 网段）

原前缀：/24
借 3 位：/24 → /27
子网掩码：255.255.255.224

② 若按 B 类默认 /16（188.12.0.0/16 再划 8 个子网）

原前缀：/16
借 3 位：/16 → /19
子网掩码：255.255.224.0

一般这类题如果明确写“188.12.1.0 网段”而不提类，通常按 /24 → 255.255.255.224 来答。

質問

思考

Rethinking the network class and subnetting

Deciding how to approach subnetting for 188.12.1.0

回答

① 若题目默认是 /24（把 188.12.1.0 当作一个 /24 网段）

② 若按 B 类默认 /16（188.12.0.0/16 再划 8 个子网）

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