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From: geertj@philica.ica.philips.nl (Geert Jan de Groot)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Proxy ARP question
Message-ID: <821@philica.ica.philips.nl>
Date: 31 May 91 23:59:10 GMT
References: <97879@lll-winken.LLNL.GOV>
Reply-To: geertj@ica.philips.nl (Geert Jan de Groot)
Organization: Philips TDS, Innovation Centre Aachen
Lines: 28

In article <97879@lll-winken.LLNL.GOV> wiltzius@lll-crg.llnl.gov (Dave Wiltzius) writes:
>I have searched the host requirements documents, rfc1009 and other
>RFCs without finding a definitive answer to the following:  Should
>proxy ARP work only for hosts on the same network, but different
>subnets?  In particular, should it specifically *not* work between
>hosts on different networks (such as 128.100 and 128.99)?

It probably doesn't work because the 'client' (ARP-requestor) has
no reason to ARP for a host that is not on his network. Foreign
networks should be routed, not proxy-arped.

The only reason why proxy arp works with subnetting is because a
client (wrongly) assumes he can reach the other host on the same
network and therefore ARPs instead of routes. This assumption was
made by older software that did not do subnetting. I have never 
seen software that didn't route for foreign networks.

If you can get your client software to ARP for foreign networks,
then I guess proxy-arp will work.

Geert Jan


--8<--nip-nip---------------------------------------------------------------

Geert Jan de Groot, Philips ICA, Weisshausstrasse 1, 5100 Aachen, Germany
Email: geertj@ica.philips.nl or ..!hp4nl!philica!geertj
Phone: +49 241 6003 714  FAX: +49 241 6003 709