According to Steven Vetzal:
>
>I'm not sure that I adequately described my situation...
>
>  [Router]---isdn---[Bridge]---ethernet---[Server]---slip---[Remote]
>204.191.16.1      204.191.16.253     204.191.16.2 ed0     204.191.16.3
>                                     204.191.16.9 sl0
>|                                             |                      |
>+------Physical Network #1--------------------+-Physical Network #2--+
>

Much clearer thank-you.

>On each physical network, I have complete connectivity. Between the 
>networks, however, there is no connection. Do I have to manually set up 
>some kind of gateway between 204.191.16.2 and 204.191.16.9 (ed0-sl0)?


No, that is already done by the slip login stuff setting up the route.
What you are seeing (i.e. being able to reach the server) proves this.

>I've even (through OS/2) explicitly done "route add 204.191.16.2 
>204.191.16.9" for the Remote host, and the remote still can't see the 
>other network... 
>

This is correct.  The major problem you have is that the Router and
the Bridge don't know how to route to Remote.  What you need to do on
the Router (and probably the Bridge) is their equivalent of:

route add 204.191.16.3 204.191.16.2 2

So that the router and bridge _know_ that to reach Remote they need to
forward packets to Server otherwise the router and bridge will just
see the packets being destined for the 204.191.16 network and put them
out on that interface.  Server will not look for these packets and
forward them to Remote the router needs to point the packets for
Remote at Server which will then hand them on.

It helps a lot if you draw a diagram and play router yourself.
Remember that you only pay attention to packets that have your address
(there are some exceptions like broadcasts but ignore those for the
moment).  Use the routing table to determine which interface the
packet goes out on.  If there is a gateway then forward the packet to
that gateway for further routing.  Then try and get a packet to it's
destination this should show you how your routing works (or doesn't).

Clear as mud?  That's routing for you :-)

-- 
Brett Lymn, Computer Systems Administrator, AWA Defence Industries
===============================================================================
"It's fifteen hundred miles to Ankh-Morpork" he said.  "We've got
three hundred and sixty three elephants, fifty carts of forage, the
monsoon's about to break and we're wearing ... we're wearing ... sort
of things, like glass, only dark... dark glass things on our eyes..."
        - Terry Pratchett "Moving Pictures".