🚀 go-pugleaf

In article <34nsfs$krr@vixen.cso.uiuc.edu>,  <dlmeyer@uiuc.edu> wrote:
(and described a clever way using proxy arp and a subnetted subnet to
handle the routing of a home LAN via SLIP to an office machine and 
thence to the world.)

>                                     SLIP link
>    L1 ------------------- L2/S1-------------------S2/I1---(office net)
>
>On L2, I set up a proxy arp for S2.
>
>On I1, I set up proxy arps for L1, L2, & S1.  (I'm not sure, S1 is needed here...)

I think all you need on I1 would be proxies for S1 and L1.  No one on
the office net needs to talk to the L2 interface.

>Now, for routing commands beyond the defaults set up through ifconfig:
>
>On I1:
>   route add L1 S1 1
>   route add L2 S1 1

I think these would be better (at least more logical to me) as:
    route add host L1 S1 1
    (nothing needed for L2, but the nameserver on the office net should
    favor the S1 interface for L2/S1)

>Now for the finer points - namely how does one localize the networks when the 
>SLIP modems are not connected?  That I have yet to figure out...

I don't think you should have to do anything.  Machines that try to
communicate across the gap would get "host unreachable" or "network
unreachable", but that is unavoidable.

>Don Meyer               Network Manager 
                         ***************

Yes, well that makes it a lot easier to obtain the addresses in the
range you need.  I know on our network if someone asked for 5 
addresses on the same subnet, they might get them but they likely
would be scattered all over the range.

I spent some time trying to think of a way to do this without any
special addressing restrictions (mainly cause I wasn't swift enough
to think of it).  I came up with something, but I'm pretty dubious
about it.  It would depend on the internal workings of your routing
software.  (I need to look at some source code, but I don't know 
when I'll have time for it.  In any case, I don't have access to
the OS/2 IP code.)

All addresses, including the office net, would be on the same subnet.
Normally that would make L1, for example, use arp to try to find any
machine on the office net.  Since I would have no hope of using
proxy arp on L2 for all those machines, I have to disable arp on the
"L" lan!

  L1 ------------------- L2/S1-------------------S2/I1---(office net)
  ifconfig lan0 L1       ifconfig lan0 L2        ifconfig lan0 I1 netmask ... arp 
   netmask ... -arp       netmask ... -arp       ifconfig sl0 S2 S1
  route add default      ifconfig sl0 S1 S2      route add host L1 S1 1
   L2 1                  route add default       arp -s S1 (hdw addr of
  arp -s L2 (hdw addr     S2 1                    I1) pub
   of L2)                arp -s L1 (hdw addr     arp -s L1 (hdw addr of
                          of L1)                  I1) pub

The "arp -s" on L1 and L2 is so that they will know how to get to
other machine on the lan (they can't use arp).  Note that the hardware
(MAC) addresses in these two commands do refer to the other machines'
adapters.

Don's technique has a big advantage in that he's actually found it to
work.  Since I don't even have a SLIP connection, everything I say
about it is guesswork.

-- 
Tony Rall    trall@almaden.ibm.com