From owner-freebsd-ipfw@FreeBSD.ORG Fri Mar 4 04:31:42 2011 Return-Path: Delivered-To: freebsd-ipfw@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id CA0B01065672 for ; Fri, 4 Mar 2011 04:31:42 +0000 (UTC) (envelope-from john@traktor.dnepro.net) Received: from smtp-out.dnepro.net (smtp-out.dnepro.net [195.24.131.41]) by mx1.freebsd.org (Postfix) with ESMTP id 50B3A8FC0A for ; Fri, 4 Mar 2011 04:31:41 +0000 (UTC) Received: from traktor.dnepro.net (localhost [127.0.0.1]) by traktor.dnepro.net (8.14.3/8.14.3) with ESMTP id p243td8m059773 for ; Fri, 4 Mar 2011 05:55:39 +0200 (EET) (envelope-from john@traktor.dnepro.net) Received: (from john@localhost) by traktor.dnepro.net (8.14.3/8.14.3/Submit) id p243tc7S059772 for freebsd-ipfw@freebsd.org; Fri, 4 Mar 2011 05:55:38 +0200 (EET) (envelope-from john) Date: Fri, 4 Mar 2011 05:55:38 +0200 From: Eugene Perevyazko To: freebsd-ipfw@freebsd.org Message-ID: <20110304035538.GA54753@traktor.dnepro.net> Mail-Followup-To: freebsd-ipfw@freebsd.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.4.2.3i Subject: ipfw fwd and multicast mac address X-BeenThere: freebsd-ipfw@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: IPFW Technical Discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 04 Mar 2011 04:31:42 -0000 Hi I've stumbled on a pretty strange issue in combination of ipfw fwd rules with multicast. The system is 7-Stable. It runs ospf, that uses MC groups 224.0.0.5 and 224.0.0.6. Normally those groups use dst mac addresses of 01:00:5e:00:00:05 and 01:00:5e:00:00:06 respectively where last 4 bytes are taken from group's IP. Then I needed to add some fwd rules like this: fwd 192.168.31.14 out xmit em0 (em0 is the interface on which ospf is running) Somehow after that MC dst mac has got 2 bytes changed: 224.0.0.5 got 01:00:5e:a8:1f:05 and 224.0.0.6 got 01:00:5e:a8:1f:06 "a8:1f" clearly is "168.31" from fwd destination. Of course this means no ospf anymore. I've fixed this by adding "pass dst-ip 224.0.0.0/8" before "fwd" but it has made my evening much more lively until I figured what's happening. The question is if this is intended consequence and if yes then why change only two bytes instead of four (irony intended)? -- Eugene Perevyazko