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From: ron@brl-sem.ARPA (Ron Natalie <ron>)
Newsgroups: net.unix-wizards,net.lan
Subject: Re: IP-Ethernet Routing Problem (4.2)
Message-ID: <414@brl-sem.ARPA>
Date: Tue, 8-Oct-85 15:14:57 EDT
Article-I.D.: brl-sem.414
Posted: Tue Oct  8 15:14:57 1985
Date-Received: Fri, 11-Oct-85 06:48:44 EDT
References: <6@uscvax.UUCP>
Organization: Ballistic Research Lab
Lines: 32
Xref: linus net.unix-wizards:12324 net.lan:923

> 
>     route add usc-cseb usc-cse
> 
> communication between usc-cse and usc-cseb stops!  (Using "telnet usc-cseb"
> 
>     Routing tables
>     Destination     Gateway         Flags    Refcnt Use        Interface
>     usc-cseb        usc-cse         UH       0      520        il0
>     loopback-net    localhost       U        0      10161      lo0
>     uscnet          usc-cse         U        1      378483     il0
> 
> Once the usc-cseb route is deleted, communication is restored.  My suspicion
> is that an ethernet interface can't handle packets routed to it as a host
> (i.e. you can have networks and gateways as destinations but not hosts).

The way the routing table works is that you give the HOST ADDRESS for the
next HOST (i.e., the gateway) that is to receieve packets bearing the ADDRESS
of DESTINTATION.

What you've done is create a loop.  Your machine will send all the usc-cseb
packets to itself continually.

> Why do we want explicit routing?  We want to use our VAX as a gateway between
> two ethernets.  Unfortunately, for reasons beyond our control, we are not
> allowed to assign different Internet network numbers to the two ethernets
> (apparently we are not allowed to have a "remote" net behind the arpanet
> gateway).

Why not check out the 4.3 Subnet code.  This is probably closer to what
you want.  Or work on some more dedicated Gateway/ARP code.

-Ron