RFC 2317:Classless IN-ADDR.ARPA delegation
RFC-Ref

IP address


Click on the red underlined text to get to the source

... objections to subnet on non-octet boundaries but perhaps more significantly, make it possible to assign IP address space in smaller chunks than 24-bit prefixes ...


... shared the same physical subnet (and corresponding IP address space) with no "neat" alignment of the addresses, but still wanted to ...



Google
Web
RFC-Ref