From owner-freebsd-net@FreeBSD.ORG Fri Oct 30 22:37:26 2009 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 20DAE1065679 for ; Fri, 30 Oct 2009 22:37:26 +0000 (UTC) (envelope-from cswiger@mac.com) Received: from asmtpout018.mac.com (asmtpout018.mac.com [17.148.16.93]) by mx1.freebsd.org (Postfix) with ESMTP id 0E8B88FC08 for ; Fri, 30 Oct 2009 22:37:25 +0000 (UTC) MIME-version: 1.0 Content-transfer-encoding: 7BIT Content-type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Received: from cswiger1.apple.com ([17.227.140.124]) by asmtp018.mac.com (Sun Java(tm) System Messaging Server 6.3-8.01 (built Dec 16 2008; 32bit)) with ESMTPSA id <0KSC00BC2MUDW590@asmtp018.mac.com> for freebsd-net@freebsd.org; Fri, 30 Oct 2009 15:37:25 -0700 (PDT) Message-id: From: Chuck Swiger To: Sebastian Hyrwall In-reply-to: <4AEB834D.1050907@keff.org> Date: Fri, 30 Oct 2009 15:37:25 -0700 References: <4AEB7AE8.5090101@keff.org> <18C758A7-1908-4D1A-BDCA-80FF7FD8BC22@mac.com> <4AEB834D.1050907@keff.org> X-Mailer: Apple Mail (2.936) Cc: freebsd-net@freebsd.org Subject: Re: Hi. /31 on ethernet links 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: Fri, 30 Oct 2009 22:37:26 -0000 On Oct 30, 2009, at 5:22 PM, Sebastian Hyrwall wrote: >> A /31 subnet is only defined for point-to-point network links, per: >> >> http://www.rfc-editor.org/rfc/rfc3021.txt >> >> Ordinary ethernet links have BROADCAST flag set instead of >> POINTOPOINT. >> > > Well how do I set the POINTOPOINT flag and remove the BROADCAST-flag > on ethernet links? Or are you implying that it does not belong on > ethernet links :) Cause Cisco and Linux support /31 (ptp's) on > ordinary ethernet links. Ethernet point-to-point links are normally handled by ppp / pppd in PPPoE mode, but possibly something like: ifconfig en0 inet 192.1.1.10 inet 192.1.1.2 ...would give you a POINTOPOINT link instead. If not, you can probably fake things out by either using a /30 and wrapping the /31 inside, or using a /32 and an explicit default route via your ethernet interface. Regards, -- -Chuck