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From: dnwcv@dcatla.UUCP (William C. VerSteeg)
Newsgroups: comp.protocols.tcp-ip
Subject: Reverse Path Forwarding (or broadcasting with subnets)
Summary: Are there routers that implement this properly???
Message-ID: <13316@dcatla.UUCP>
Date: 20 Jan 89 15:31:23 GMT
Reply-To: dnwcv@sune.UUCP (William C. VerSteeg)
Organization: DCA Inc., Alpharetta, GA
Lines: 27


We are in the process of porting a proprietary PC networking 
system to an IP based system. One of the thing we would like to
do is use IP routers to forward broadcast messages to "all nodes"
of our network. We are defining "all nodes" to be "all systems
on my (subnetted) network". When a node broadcasts to the network address,
RFC922 states that routers should forward this broadcast to all
applicible networks. In other words, the broadcast 36.255.255.255
should reach all members of (subnetted) network 36, whether
they live on the same ethernet cable as the broadcaster or not.


I have noticed that some routers do not implement the 
algorithm (Reverse Path Forwarding) that allows this to happen.

Does anyone know of an implementation 
that does reverse path forwarding?


Bill VerSteeg
DCA
1000 Alderman Drive
Alpharetta Ga. 30201

P.S. To the vendor to which I have been talking about this problem-
     Notice how nice I was here and didn't shamelessly rake you over 
     the coals in public. Wasn't that nice?