Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!mips!sgi!vjs@rhyolite.wpd.sgi.com
From: vjs@rhyolite.wpd.sgi.com (Vernon Schryver)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Question on forwarding broadcasts
Message-ID: <70667@sgi.sgi.com>
Date: 28 Sep 90 23:40:10 GMT
References: <1990Sep28.143945.7440@ultra.com>
Sender: guest@sgi.sgi.com
Organization: Silicon Graphics, Inc., Mountain View, CA
Lines: 33

In article <1990Sep28.143945.7440@ultra.com>, wayne@ultra.com (Wayne Hathaway) writes:
> ... [description of having 2 logical networks on 1 cable deleted]
>...
> Clearly what Host B SHOULD do with the "misdelivered broadcast" is say
> "This is not for me AND it came in as a MAC layer broadcast; therefore
> just discard it (do NOT forward it)."  But unfortunately that requires
> IP to know what MAC layer address a datagram came in on, and (at least
> in any BSD-derivative implementation I know of) that information is
> not available to IP.

I think this is available in 4.3BSD-Reno.  I think it is required
by the Host Requirements RFCs.  It is or will soon be available from
at least one vendor.

>...
> Finally, note that saying "Host B should recognize this is a broadcast
> from the destination address and not forward it" is NOT a solution,
> since it appears to Host B to be a perfectly legal DIRECTED broadcast
> to network 192.40.1 from somewhere else, and as far as Host B knows,
> he is the only way for that directed broadcast to get through; he HAS
> to forward it.
>...
>     Wayne Hathaway               domain: wayne@Ultra.COM
>     Ultra Network Technologies     uucp: ...!ames!ultra!wayne


What about using any of the zillions of routing protocols instead
of static, default routes?  Even RIP should work.

I thought some people say directed broadcasts are or should be illegal.


Vernon Schryver,  Silicon Graphics,   vjs@sgi.com