Strange network problem

[Gerald Combs]

Monty J. Harder wrote:
> "Gerald Combs" <gerald at zing.org> wrote:
> 
> 
>>>netmask is 172.21.12.255 which is correct.
>>
>>It is?  Subnet masks are nearly always a string of ones, followed by a
>>string of zeroes, e.g. "255.255.255.0".  The ones indicate which bits in
> 
> 
>   'Usually'?  When are they not?

A while back I heard about a product that would "scramble" MAC
addresses, IP addresses, and netmasks on a local subnet in order to
secure it from intruders.  As I recall, one of the "tricks" it used was
non-contiguous subnet mask bits.

AFAIK, the convention of a contiguous set of ones followed by a
contiguous set of zeroes isn't explictly mandated, but it makes routing
not only easy, but possible.  Which mask indicates the best path:
255.255.255.0 or 255.255.0.128?

Aside from adding a lot of (needless) complexity to your network, this
scheme also means you can't use CIDR notation.