From owner-freebsd-bugs Wed Aug 19 06:41:35 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id GAA11309 for freebsd-bugs-outgoing; Wed, 19 Aug 1998 06:41:35 -0700 (PDT) (envelope-from owner-freebsd-bugs@FreeBSD.ORG) Received: from cal007109.student.utwente.nl (cal007109.student.utwente.nl [130.89.221.199]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id GAA11258; Wed, 19 Aug 1998 06:41:22 -0700 (PDT) (envelope-from edwin-ml@woudt.nl) Received: from [192.168.1.2] (helo=desktop) by cal007109.student.utwente.nl with smtp (Exim 2.02 #2) id 0z98Sg-0001u7-00; Wed, 19 Aug 1998 15:39:38 +0200 From: "Edwin Woudt" To: Edwin Woudt , Peter Hawkins Date: Wed, 19 Aug 1998 15:42:47 +0100 MIME-Version: 1.0 Content-type: text/plain; charset=US-ASCII Content-transfer-encoding: 7BIT Subject: Re: Gateway/firewall denial of service Reply-to: edwin@woudt.nl CC: freebsd-security@FreeBSD.ORG, freebsd-bugs@FreeBSD.ORG References: In-reply-to: X-mailer: Pegasus Mail for Win32 (v3.01a) Message-Id: Sender: owner-freebsd-bugs@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org > In general, when duplicate IPs are assigned on a segment, the router > will commence routing to the new MAC address after it is ARPed which > is precisely what FreeBSD did for you. Locking an address doesn't really > constitute a solution as the router cannot determine which of the two > machines has the correct mac address - one could deny service permanently > by booting first. Flipping the mac address is correct as the most common > cause of a mac address change is quite innocuous - a machine has been > shut down for an ethernet card swap and rebooted. Locking an address to > a mac address would make it very difficult to change ethernet cards in > machines. Those duplicate IP's are not on the same segment. My local computer is on my local segment (192.168.0.0/16). This segment is connected to network card 'ep1'. The problem is that it accepts new MAC addresses for this segment on the other interface: 'ep0'. Though it changes the MAC address, it doesn't change the interface in teh routing table. So after this happends it tries to contact my local machine via ep1, but the MAC address in it's routing table is from a network card on ep0 (the campus network). Edwin Woudt ===================================================================== Edwin Woudt ("`-''-/").___..--''"`-._ Calslaan 7-109 `6_ 6 ) `-. ( ).`-.__.`) 7522 MH Enschede edwin@woudt.nl (_Y_.)' ._ ) `._ `. ``-..-' The Netherlands _..`--'_..-_/ /--'_.' ,' ICQ: 1156462 (il),-'' (li),' ((!.-' +31 53 489 5010 ===================================================================== To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-bugs" in the body of the message