From mboxrd@z Thu Jan 1 00:00:00 1970 From: Denys Fedoryschenko Subject: Re: [RFC] arp announce, arp_proxy and windows ip conflict verification Date: Fri, 3 Jul 2009 14:02:34 +0300 Message-ID: <200907031402.34941.denys@visp.net.lb> References: <200903011344.45814.denys@visp.net.lb> <200907030246.18054.denys@visp.net.lb> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, David Miller To: "Eric W. Biederman" Return-path: Received: from hosting.visp.net.lb ([194.146.153.11]:41668 "EHLO hosting.visp.net.lb" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751484AbZGCLCu (ORCPT ); Fri, 3 Jul 2009 07:02:50 -0400 In-Reply-To: Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: On Friday 03 July 2009 06:14:44 Eric W. Biederman wrote: Actually problem doesn't worth a broken egg even. I am not confused. Just i am trying to explain that some feature implementation must follow standards somehow, especially because it break things. And it breaks. Actual use for proxy_arp in modern world is very small, and i think it is used rarely, only for PPP links for remote customers. But even in this case it will break things, if this box have default gateway. 1)If Linux have default gateway configured "some other" interface, enabling proxy_arp on ethernet interface will break communication for any network that is not configured on this Linux interface. It will just give ARP reply for all ARP requests. 2)ACD (Address conflict detection) used in DHCP, Mobile IP and etc, and it uses gratituous ARP/ARP Announce. Proxy ARP used to help route networks. Gratituous ARP/ARP Announce packet have no use for routing, it is for ACD and ARP cache updating (for clusters). Linux ARP proxy gives answer to such packets, which doesn't have use for routing, but breaks ACD (gives false positive ip conflict). Anyway, i ask advice from one of RFC authors. I will forward it here as soon as receive it.