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From: pdb@sei.cmu.edu (Patrick Barron)
Newsgroups: comp.unix.wizards
Subject: Re: rwho problems between 4.2 and 4.3 hosts
Message-ID: <1413@aw.sei.cmu.edu>
Date: Mon, 25-May-87 21:22:11 EDT
Article-I.D.: aw.1413
Posted: Mon May 25 21:22:11 1987
Date-Received: Sat, 6-Jun-87 12:48:56 EDT
References: <7523@brl-adm.ARPA>
Sender: netnews@sei.cmu.edu
Reply-To: pdb@sei.cmu.edu (Pat Barron)
Organization: Carnegie-Mellon University, SEI, Pgh, Pa
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In article <7523@brl-adm.ARPA> esj%bikini.cis.ufl.edu@RELAY.CS.NET (Eric Johnson) writes:
>	  We recently changed our network numbers to our assigned class
>	B address. Before we did this the 4.2 hosts saw all (including
>	4.3 hosts) packets. 
>	  A Excelan Lanalyzer shows that after each host broadcasts a 
>	rwho packet, the 4.2 hosts send back a 
>		icmp: UNREACH NET
>	packet. 

I've seen something like this just recently.  4.2 hosts didn't like broadcast
packets sent by hosts with 4.3-like networking (specifically, Ultrix 1.2).
One of the 4.2 hosts was sending ICMP network unreachable messages in response
to each, and the rest (Suns running Sun Unix 3.2) were trying to forward the
packet.  Problem was that the Ultrix machines and the 4.2 machines had differ-
ing ideas about what the IP broadcast address was.  The Ultrix machines thought
it was (in our case) 128.2.255.255, and the 4.2 machines thought it was
128.2.0.0.  You might want to check to make sure your broadcast addresses
agree.  4.3bsd will allow you to change to IP broadcast address with ifconfig.

--Pat.