From owner-freebsd-arch@FreeBSD.ORG Tue Nov 8 00:49:33 2005 Return-Path: X-Original-To: arch@freebsd.org Delivered-To: freebsd-arch@FreeBSD.ORG Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 2D85816A41F for ; Tue, 8 Nov 2005 00:49:33 +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 B695C43D48 for ; Tue, 8 Nov 2005 00:49:32 +0000 (GMT) (envelope-from cswiger@mac.com) Received: from localhost (localhost [127.0.0.1]) by pi.codefab.com (Postfix) with ESMTP id 1D9425DDA; Mon, 7 Nov 2005 19:49:32 -0500 (EST) 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 90417-04; Mon, 7 Nov 2005 19:49:31 -0500 (EST) Received: from [199.103.21.238] (pan.codefab.com [199.103.21.238]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (No client certificate requested) by pi.codefab.com (Postfix) with ESMTP id 0DDF95D40; Mon, 7 Nov 2005 19:49:31 -0500 (EST) In-Reply-To: <20051107234548.GF775@funkthat.com> References: <20051107140451.GU91530@cell.sick.ru> <436F7DDB.40703@mac.com> <20051107224338.GE775@funkthat.com> <20051107234548.GF775@funkthat.com> Mime-Version: 1.0 (Apple Message framework v746.2) Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Message-Id: <036D3BD4-D856-4D50-A7D3-2300EFEA604F@mac.com> Content-Transfer-Encoding: 7bit From: Charles Swiger Date: Mon, 7 Nov 2005 19:49:30 -0500 To: John-Mark Gurney X-Mailer: Apple Mail (2.746.2) X-Virus-Scanned: amavisd-new at codefab.com Cc: arch@freebsd.org, Garance A Drosihn Subject: Re: ARP request retransmitting X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 08 Nov 2005 00:49:33 -0000 On Nov 7, 2005, at 6:45 PM, John-Mark Gurney wrote: >> Really? You're saying that "tcpdump -nt arp" never shows any >> requests except those made by the local host? >> >> Which vendor and which switch model? > > Just a random search for smart arp large, turned up user's manual > for the WaveSwitch 9000, from Plaintree Systems.. > > The docs say: > Address Resolution Protocol (ARP) is the means by which a host or > router > maps an IP address to a physical address. WaveSwitch 9000 software > contains the SmartARP feature that allows for reduced impact of ARP > broadcasting. > > Normally, ARP broadcasts are flooded to all ports on a switch. Switch > ports that are not connected to the target host must, therefore, > receive > and partially process the broadcast frames. This can potentially > affect > the performance of all hosts on the bridged network. [ ... ] > A coworker also says that the Foundary switches can do it, and did > it like five years ago... I haven't confirmed this myself... OK, I appreciate the response and the pointer to a specific model. This being said, I'd prefer a first-hand account from someone who has actually run tcpdump for a few days on a production network and confirmed that this feature really works as advertised. (There can be a big difference between what the documentation claims a switch does, and what the switch actually does. In particular, switch vendors have also claimed that VLAN tagging was reliable and secure and that traffic from one VLAN could never leak to a port on another VLAN...) ----- I think your other comment about extending the lifespan of entries in the ARP cache is a more useful idea, at least for extending the lifespan of valid entries. Negative response to an ARP request should not be cached for very long. Does FreeBSD update the ARP cache when ARPOP_REQUESTs are seen? At the very least, one could refresh the timer if you have an entry for the host making the request... -- -Chuck