Re: more interesting features of 4.2


Matt Crawford (oddjob!matt@lbl-csam.ARPA)
Tue, 10 Jun 86 17:47:30 cdt


        It turns out that you can specify routing entries that
        will cause a host to treat destinations on that network
        as local. I.e. it will issue ARP's for them, just as if
        they were on the local Ethernet. The correct form is
           route add 0 <local-host-address>
        if you want to set this up as a default.

I tried "route add usan-net oddjob 0" some time ago, trying to
access the USAN satellite net through our VitaLink box. This
works to NCAR (where all hosts' addresses are on usan-net) if
they do the corresponding operation on their end. The trouble
comes when you want to specify that a host on the other net is a
gateway to yet another net. The route-adding code insists that
you can't do it.

I then wrote a pseudo-interface driver which claims an interface
address of "oddjob" (192.5.73.2) but a broadcast address of
"usan-net" (192.17.4.0). This works OK (I'm still using it),
but still has some drawbacks. One is that the other end (U of I
at Urbana in this case) would have to put up a similar pseudo-
interface on their gateway to usan-net before their networks and
our networks are fully connected. Another is that broadcasts
such as RIP packets sent to usan-net generate ICMP messages from
other hosts on the local net here.

I don't think any arrangement will really work satisfactorily if
it has bridges connecting nets with different IP numbers.

                Matt Crawford



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