> The Mac UI limited you to those three classful subnet masks. And it assumed a specific network architecture -- e.g, if you have a class A network, the middle

> The Mac UI limited you to those three classful subnet masks. And it assumed a specific network architecture -- e.g, if you have a class A network, the middle two octets of your address represent a "subnet" and the last octet represents a "node". This may have been appropriate in pre-CIDR networks where all local nets were /24, but it's no longer true today; it's not uncommon to have networks which split on non-octet boundaries.