*BSD News Article 84407


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From: oradya@muss.CIS.McMaster.CA (A. Orady)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Proxy ARP
Date: 6 Dec 1996 22:08:45 GMT
Organization: McMaster University, Hamilton, Ontario, Canada (NewServer)
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Message-ID: <58a5hd$hai@informer1.cis.McMaster.CA>
NNTP-Posting-Host: muss.cis.mcmaster.ca
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Hi,
	I have a setup where I am using a FreeBSD 2.1.0-RELEASE machine
with IP_FORWARDING enabled in the kernel as a gateway.  It has two ethernet
boards.  The problem is that I have configured all the machines on the
interior to use the FreeBSD machine as a gateway, but the machines
on the exterior do not know its a gateway... I need to use proxy-ARP so that
the machines on the exterior send thier packets to the gateway.  I have
tried adding a "pub" arp entry, i.e., 

arp -s "interior_host1" "exterior_gateway_eth_addr" pub

This causes the system to respond to ARP request on the exterior network 
which are looking for a host on the interior.  It sends the MAC address
of the exterior ethernet board in the reply, that way, the packets
are sent to the gateway, and are then routed to the interior.  The only 
problem is that this also causes the FreeBSD system to respond to ARP
requests on the interior network!  Is there any way to setup a proxy-arp
which will only respond to requests on one interface?

Thanks in advance,
Aly