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Date:      Tue, 29 Aug 1995 12:00:07 +0930 (CST)
From:      Michael Smith <msmith@atrad.adelaide.edu.au>
To:        SimsS@Infi.Net
Cc:        hackers@freebsd.org, apuzzo@alumni.cs.colorado.edu, davep@extendsys.com, rgrimes@gndrsh.aac.dev.com
Subject:   Re: ARP'ing [Summary of responses]
Message-ID:  <199508290230.MAA24552@genesis.atrad.adelaide.edu.au>
In-Reply-To: <199508281259.FAA29765@freefall.FreeBSD.org> from "Pavlov's Cat" at Aug 28, 95 08:59:53 am

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Pavlov's Cat stands accused of saying:
> same address (192.168.254.130) because it's the first free entry in it's
> dynamic pool.  (N.B.: DHCP servers don't have a way to monitor addresses
> which are "in use" but weren't asssigned by the DHCP server.)  The client
> accepts the offered address and (at least with WinDoze clients) attempts to
> ARP the wire for "192.168.254.130" since it doesn't explicitly "trust" the server. 
> Whoops!  The client "discovers"  that the address is already in use! 

Pick a DHCP server you have source for, and get it to arp around before
it allocates the IP number.  If it finds it, you have a few options :
you can try to kill the offender (arp loudly for the same address and hope
that they go offline as a result - this works well in some cases 8),
or you can just log an irate message and try again later.
(This would also be useful for retrieving state after a DHCP server restart)

> Systems Engineer, IPC Technologies, Inc.          Virginia Beach, VA

-- 
]] Mike Smith, Software Engineer        msmith@atrad.adelaide.edu.au    [[
]] Genesis Software                     genesis@atrad.adelaide.edu.au   [[
]] High-speed data acquisition and                                      [[
]] realtime instrument control          (ph/fax) +61-8-267-3039         [[
]] My car has "demand start" -Terry Lambert  UNIX: live FreeBSD or die! [[



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