🚀 go-pugleaf

Back to 2 subnets on 1 segment again:

Greetings,

I was wondering if anyone might have any insight
into the following situation that involves 2 subnets
on the same ethernet segment:

Given the following setup:

net 140.140.1.0 subnet mask 255.255.255.0
net 140.140.2.0 subnet mask 255.255.255.0

The local topology is something like this:

default router:
		aix box  1.100
		  |
	cisco ---------------- subnets 1 and 2 (same wire) -------
					 | zymurgy
					 1.240/2.240

We have an experimental server on zymurgy that is sending 
out a directed broadcast on net 2 as 140.140.2.255. 
Zymurgy has the capability to have 2 ip addresses
attached to a single enet device.
		140.140.1.240
		140.140.2.240
It is sending the directed bcast out to 2.255 as an
ethernet bcast.

So anyway we have the real net '1' and the experimental
subnet on top of it, '2'. 

For "no apparent reason" an aix box and an hp X terminal too 
(both on net 1 with 1 interface and 1 ip address on that
interface)
are picking up the directed broadcast and forwarding it
as a unicast packet to the "default" cisco router.
Why a broadcast on another ip subnet is forwarded
is beyond me. The aix box is forwarding the packet too (
ip ttl is decremented; netstat -s shows forwarding count
incremented ). (Of course, it also happens
to not be a router in the real sense of the word -
The cisco then forwards
the unicast back to zymurgy but it has been told
already (via static routes) to forward any
default net 2 subnet packets to zymurgy -- so that is the
correct move. Nothing but static routes -- no rip or
any kind of dynamic routing used here.
Any insights here?  Mine is: "Life with 2 subnets
in the presence of buggy tcp/ip implementations can be
interesting :->"

			Jim Binkley
			jrb@cs.pdx.edu