Date: Mon, 11 Nov 2013 14:59:37 +0000 From: Karl Pielorz <kpielorz_lst@tdx.co.uk> To: freebsd-net@freebsd.org Subject: IP clash (arp: x is using my IP address y on em1!) - recovering? Message-ID: <5F431BB1ED5D1F3DB12CF1AD@Mail-PC.tdx.co.uk>
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Hi, I've got a couple of FreeBSD boxes (9.2-R). I just accidentally brought 'up' the same IP address on both. Sure enough the console logs a bunch of "arp x is using my IP address y on ..." style messages. I quickly took down the 'new' IP's on one box (in fact, I shut the whole box down). However the original box with the addresses stopped responding to traffic going to those addresses. I flushed the ARP table on another box - and tried pinging one of the IP's that clashed - and you get nothing back. You don't event get an ARP entry appearing for it - i.e. if both boxes are on the same LAN / IP address range. It'll quite happily respond to other IP's (on the same interface / MAC) - but not the one that got 'clobbered'. In the end I 'ifconfig' deleted the clashed IP's off the original box - and added them again to the same box. This seems to have resolved it. Is there some way of avoiding this in the future? - I guess it's some kind of 'defensive' move or something? - We've just never seen it in the past (the very occasional times we've brought up two IP's it's been on much older boxes). -Karl
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