SunOS & non-uniform subnet masks..

[andyw@ironwood.cray.com (Andy Warner)]

Given the following (simplified) setup:

        +-----------+                 +----------+
        | SunOS     |     ethernet    | NOS      |---- 1200/9600 radio links
        | 44.n.n.n  |-----------------| 44.n.n.m |     connected to 44.x.x.x
        +-----------+                 +----------+
              |
              |
              |
          +-------+
          | Phone |
          | Modem |
          +-------+


The Sun and the NOS box are on a small subnet of net-44, and the
default route for the Sun is set to be the NOS router.
This works just fine, until the modem is used to get a PPP connection
to the internet; then the default route becomes ppp0 (the PPP interface.)
It is not possible to set a route to 44.0.0.0/8 under SunOS, in fact
there is some quaint code that makes the assumption that within a
network, all subnet masks are identical. Since le0 has a subnet mask
and is part of the class A net-44, SunOS applies that netmask to the
route too, hence some miniscule part of net-44 remains accessible.
I realise that in theory, the internet-connected hosts on net-44
may remain available (subject to firewalls), but in reality any
open connections to 44.x.y.z go into deep-freeze.

I hear that BSD 4.4 has a more powerful routing subsystem (patricia
trees?) that propogates subnet masks, but short of re-writing in.c and
route.c, are there any other options ? At the moment, as soon as the
PPP link goes online, the SunOS box vanishes from the radio network
(which is a shame, since it is a mail-hub and DNS server.)

-- 
andyw.	N0REN/G1XRL

andyw@aspen.cray.com	Andy Warner, Cray Research, Inc.	(612) 683-5835