It depends. If you are using a classless routing protocol, you can
certainly use these subnets. If you are using a classful routing
protocol, then it depends on the vendor platform and if they have
a mechanisn that supports explicit use of these subnets.
A word of caution is needed, however, since using them is not
RFC compliant. :-)
Actually, I got that changed in router requirements RFC. We (the IETF)
officially depricated the reserved status of the all zero's and all one's
subnets in a "classless" environment.
So, it's official now.
We currently warn people if they try to assign an interface to an "all zeros"
subnet because most other router vendors don't properly handle classFUL
routing protocols like RIP in this situation...in fact, we can't guarantee
that we'll always do exactly the right thing (it can be hard to figure out).
To disable the warning, just configer "ip subnet-zero" and the router will
let you configure subnet zero addresses. (hmmm, I should hang that on ip
classless too...type type type...).
- other paul