From owner-freebsd-questions  Tue Jun 23 01:45:20 1998
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Date: Tue, 23 Jun 1998 01:44:56 -0700 (PDT)
From: Doug White <dwhite@resnet.uoregon.edu>
To: Dan Busarow <dan@dpcsys.com>
cc: Jeremy Shaffner <jer@jorsm.com>, Eddie Irvine <eirvine@tpgi.com.au>,
        freebsd-questions@FreeBSD.ORG
Subject: Re: Proxy arp - what is it?
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On Mon, 22 Jun 1998, Dan Busarow wrote:

> On Mon, 22 Jun 1998, Jeremy Shaffner wrote:
> > proxy arp is when one computer answers arp (IP <-> Ethernet
> > Address) requests for another computer.
> 
> Just to expand on that a little bit.  Ethernet really works
> using ethernet hardware addresses (MAC addresses), not IP 
> addresses (fancy that :)  Since most modems don't have MAC
> addresses the host providing dialup service supplies its own
> enet hardware address in response to arp requests for the modem's
> IP.

And a bit more ..

You need to run proxy ARP if you're, say, dialed into a modem pool that
assigns IPs from one subnet, so that the ends of the link are on the same
subnet by IP.  The problem is that ARP requests won't flow over the dialup
link to your machines on the client side of the link.  Proxy ARP will
forward the requests over the dialup link so the clients know who to talk
to.

Doug White                              | University of Oregon  
Internet:  dwhite@resnet.uoregon.edu    | Residence Networking Assistant
http://gladstone.uoregon.edu/~dwhite    | Computer Science Major


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