🚀 go-pugleaf

 
>               But  for some reason  (perhaps some subnetting  rule),
> the cisco will  to not accept  two *different* subnet  masks for the
> same class B  network.  The cisco  automatically changes the  subnet
> mask for all interfaces with the same class B network address to the
> last subnet mask of the last interface set.

According to RFC 950 only one subnetmask is allowed for an IP network:

      For example, the Internet address might be interpreted as:

         <network-number><subnet-number><host-number>

      where the <network-number> field is as defined by IP [3], the
      <host-number> field is at least 1-bit wide, and the width of the
      <subnet-number> field is constant for a given network.  No further
                               ----------------------------
      structure is required for the <subnet-number> or <host-number>
      fields.  If the width of the <subnet-number> field is zero, then
      the network is not subnetted (i.e., the interpretation of [3] is
      used).

We have the same problem as you and waste a lot of our Class B
address space because of this. I have heard some rumors that new
routing protocols (OSPF ?) could solve this problem by carrying a 
variable subnet mask information with them.

-- Peter

Peter Merdian, BelWue Coordination, University of Stuttgart, merdian@belwue.de