Path: utzoo!attcan!uunet!samsung!usc!apple!motcsd!hpda!hpcuhb!hpindda!dfc
From: dfc@hpindda.HP.COM (Don Coolidge)
Newsgroups: comp.sys.hp
Subject: Re: Inquiry about broadcasting an address on a HP9000/320 (6.2 HP-UX)
Message-ID: <4310077@hpindda.HP.COM>
Date: 1 Dec 89 20:12:58 GMT
References: <1070@mit-amt.MEDIA.MIT.EDU>
Organization: HP Information Networks, Cupertino, CA
Lines: 25

>There's only one way I can conceive of that other nodes on your LAN could
>be seeing 18.0.0.0 - if you have an application using sendto() with 18.0.0.0
>specified as the target IP address.

>By the way, even though the interface broadcast address is defaulted to all
>ones, HP-UX will also recognize inbound and outbound datagrams with all zeroes
>as valid broadcast packets.

I've received some private email describing the problem in greater detail,
and wanted to post the final answer. The problem is rwhod, which is using
sendto() as I described above. HP's released networking code is based on 
4.2BSD, which used zeroes as a broadcast address. We've made many 4.3-ish
upgrades, but rwhod has not yet been one of them. Unforunately, the address
used by rwhod's sendto() is hard-coded in 4.2-ish zeroes.

So, for the systems mentioned in the original posting (6.0, 6.2), rwhod will
continue to pump zero-based packets onto the net unless you invoke it with
the -r flag (receive data only; don't send any). 

Administrators of large LANs might want to keep rwhod generally inactive,
anyway (on all machines, not only on HP systems) - large numbers of broadcasts
(one/node/3 minutes) unnecessarily eat up a lot of LAN and machine bandwidth
on LANs with lots of nodes.

- Don Coolidge