Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cornell!uw-beaver!fluke!ssc-vax!bruce
From: bruce@ssc-vax.UUCP (Bruce Stock)
Newsgroups: comp.protocols.tcp-ip
Subject: Proxy Arp -- How is it Implemented?
Keywords: RFC925
Message-ID: <2552@ssc-vax.UUCP>
Date: 28 Mar 89 18:00:25 GMT
Distribution: usa
Organization: Boeing Aerospace Corp., Seattle WA
Lines: 23


After reading many references to the use of proxy arp, I decided to consult
RFC 925 to get the details.  The description there did not match the
mechanism I had mentally envisioned from descriptions of what proxy arp does.

In brief, the RFC describes a mechanism for extending the arp reply service
by expanding the arp cache in the gateway, via a somewhat elaborate means,
to include end systems which the gateway can get to on other networks.  

From reading about the service offered by proxy arp elsewhere, I had
assumed that a gateway would implement it not by an expansion of the arp cache,
but by coupling arp with the routing table.  E.G.:
	1. Recieve Arp request
	2. Consult routing table to see if I can reach the destination
	3. If I can, reply to the arp with my physical address
	4. If not, do nothing.

So my question is:  How is it done in the real world?  Per RFC925, per above,
or otherwise?


		Regards,  Bruce Stock
			uw-beaver!ssc-vax!bruce