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  • Hirofumi Takahashi thinks this is interesting:

The second caution has to do with the verbal description of subnets and their masks. Subnetting the third octet of a Class B address, as is done is Figure 1-7, is very common; also common is hearing people describe such a subnet design as “using a Class C mask with a Class B address,” or “subnetting a Class B address into a Class C.” Both descriptions are wrong! Such descriptions frequently lead to misunderstandings about the subnet design or to a poor understanding of subnetting itself....

From

Cover of Routing TCP/IP, Volume 1, 2/e

Note

Description to subnet Class B address with 255.255.255.0