In message <19990302104412.B6605@noc.untraceable.net> Andrew Brown wrote:
>on a slightly different note...does anyone have any clue why ciscos
>refuse to allow you to use an "all zeros" subnet mask (ie, the
>interface address 206.223.36.7/25 is illegal since the subnet mask is
>a single zero bit) unless you explicitly say "ip subnet-zero"?

Just leftover classful cruft.  The IOS documentation says:

    Subnetting with a subnet address of zero is discouraged because
    of the confusion inherent in having a network and a subnet with
    indistinguishable addresses.

(i.e. if you're not very smart, you can't tell the difference between
13.0.0.0 referring to the class A network 13/8 and 13.0.0.0 referring
to the subnet 13.0.0/22.)

  Bill