netdev - Re: [RFC] arp announce, arp_proxy and windows ip conflict verification

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Message-ID: <m1y6r6wwxy.fsf@fess.ebiederm.org>
Date:	Thu, 02 Jul 2009 15:18:33 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Denys Fedoryschenko <denys@...p.net.lb>
Cc:	netdev@...r.kernel.org, David Miller <davem@...emloft.net>
Subject: Re: [RFC] arp announce, arp_proxy and windows ip conflict verification

Denys Fedoryschenko <denys@...p.net.lb> writes:

> If i have two networks proxy arp'ed
> 10.0.0.0/24 physical segment
> 10.0.1.0/24 physical segment
>
> proxy_arp host between them, so users can set on their laptops /22 and 
> communicate freely like they are in one segment.
>
> Some user with XP on laptop with ip 10.0.0.66/22 will come to 10.0.1.0/24 
> physical segment. As second he will turn on his laptop - proxy_arp host will 
> give him incorrect answer to his ARP announce "10.0.0.66 (ff:ff:ff:ff:ff:ff) 
> tell 10.0.0.66", it will tell "Reply 10.0.0.66 is-at 52:54:00:12:34:56" - 
> that IP is busy. And thats wrong. arp_proxy should help hosts to communicate, 
> but should not give incorrect answers that ip is taken.

The problem is you have machines on the wrong subnet.

If you are not enforcing which network your laptops are in you
want ethernet bridging not proxy_arp.

Eric

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