From owner-freebsd-net@FreeBSD.ORG Sun Sep 18 16:14:02 2005 Return-Path: X-Original-To: freebsd-net@freebsd.org Delivered-To: freebsd-net@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 63C8D16A41F for ; Sun, 18 Sep 2005 16:14:02 +0000 (GMT) (envelope-from cswiger@mac.com) Received: from pi.codefab.com (pi.codefab.com [199.103.21.227]) by mx1.FreeBSD.org (Postfix) with ESMTP id 04DC743D45 for ; Sun, 18 Sep 2005 16:14:01 +0000 (GMT) (envelope-from cswiger@mac.com) Received: from localhost (localhost [127.0.0.1]) by pi.codefab.com (Postfix) with ESMTP id 79BF95D8C; Sun, 18 Sep 2005 12:14:01 -0400 (EDT) Received: from pi.codefab.com ([127.0.0.1]) by localhost (pi.codefab.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 04044-02; Sun, 18 Sep 2005 12:14:00 -0400 (EDT) Received: from [192.168.1.3] (pool-68-161-68-11.ny325.east.verizon.net [68.161.68.11]) by pi.codefab.com (Postfix) with ESMTP id BCFE85C70; Sun, 18 Sep 2005 12:13:59 -0400 (EDT) Message-ID: <432D9249.9090202@mac.com> Date: Sun, 18 Sep 2005 12:14:01 -0400 From: Chuck Swiger Organization: The Courts of Chaos User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.11) Gecko/20050728 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Motonori Shindo References: <20050919.004531.92589257.mshindo@mshindo.net> In-Reply-To: <20050919.004531.92589257.mshindo@mshindo.net> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: amavisd-new at codefab.com Cc: freebsd-net@freebsd.org Subject: Re: ARP behavior in FreeBSD vs Linux X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 18 Sep 2005 16:14:02 -0000 Motonori Shindo wrote: > On FreeBSD (and I guess most Operating Systems as well), ARP reply is > sent back only when the target IP address in ARP request matches with > one of the IP addresses assigned to the interface through which the > ARP Request is received. This is correct behavior. Normally, you should only be able to ARP an IP address which is on an interface connected to that subnet. > In contrast, on Linux (by default), it > responds as long as the target IP address in ARP Request matches with > any "local" IP address on the system, which is not necessarily an IP > address assigned to the interface through which the ARP request is > received. This sounds like "proxy ARPing" is enabled by default on your particular flavor of Linux. I don't think they all do that, hopefully, any more than ipforwarding should be enabled by default just because a machine has two NICs. > Is there any advantage/disadvantage in ARP implementation on FreeBSD > over that of Linux? Thanks. This information disclosure could potentially be a security problem, if Linux is providing the MAC address of a NIC not connected to the subnet without being explicitly configured to do so...although in practice very few people actually implement layer-2 security measures. -- -Chuck