Path: utzoo!attcan!uunet!lll-winken!ames!mailrus!csd4.milw.wisc.edu!uxc!garcon!tuna.cso.uiuc.edu!kline
From: kline@tuna.cso.uiuc.edu (Charley Kline)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: NFS Performance through Routers
Message-ID: <633@garcon.cso.uiuc.edu>
Date: 19 Mar 89 04:05:06 GMT
References: <237@alux2.ATT.COM>
Sender: news@garcon.cso.uiuc.edu
Organization: University of Illinois at Urbana-Champaign
Lines: 33

> There is a problem stemming from
> the fact that older versions of UNIX are trying to forward IP broadcast
> packets.  When these hosts receive a broadcasted RIP packet addressed
> to 128.94.255.255, they think it's a packet destined to a specific
> machine and they then try and forward it.  For every such packet, an
> ARP request is broadcasted on the ethernet.  There are about 16
> machines running the old network software and 5 routers generating up
> to 5 rip packets every 30 seconds.  I believe that added up to around
> 28,000 broadcasts per hour.  Temporarily, I answered these ARP requests
> and pointed them to a device that would ignore them, but the network is
> still slow.  Is there anything wrong with responding to these ARP
> requests with an ethernet address that doesn't really exist on that
> network.

Yow! Be careful with your broadcast address! If you have old Suns, they'll
be using a zero's broadcast (128.94.0.0). The p4200 by default will use
ones broadcast. I'm not surprised you're getting 28000 broadcasts an hour
and all those collisions. Mixing broadcast addresses is a good way to get
an ethernet meltdown, because exactly the behavior you describe happens.

Go to the same broadcast address everywhere on your net and I bet a lot
of your problem will go away. Since you're running old Suns, which don't
give you a choice, I suspect you'll have to change everything to zero's
broadcast.

Hope this helps.

-----
Charley Kline, University of Illinois Computing Services
kline@tuna.cso.uiuc.edu
{uunet,seismo,pur-ee,convex}!uiucdcs!uiucuxc!kline

"Flaring high or flaring early makes the little prop tips curly."