From owner-freebsd-net@FreeBSD.ORG Sat Jan 11 15:24:45 2014 Return-Path: Delivered-To: net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 7F0B26B for ; Sat, 11 Jan 2014 15:24:45 +0000 (UTC) Received: from bizet.nethelp.no (bizet.nethelp.no [195.1.209.33]) by mx1.freebsd.org (Postfix) with SMTP id 6F4F819FD for ; Sat, 11 Jan 2014 15:24:43 +0000 (UTC) Received: (qmail 7932 invoked from network); 11 Jan 2014 15:24:41 -0000 Received: from bizet.nethelp.no (HELO localhost) (195.1.209.33) by bizet.nethelp.no with SMTP; 11 Jan 2014 15:24:41 -0000 Date: Sat, 11 Jan 2014 16:24:41 +0100 (CET) Message-Id: <20140111.162441.104033349.sthaug@nethelp.no> To: thomas@gibfest.dk Subject: Re: Merge ping+ping6 and traceroue+traceroute6 to single utilities? From: sthaug@nethelp.no In-Reply-To: <52D15185.50802@gibfest.dk> References: <52D14140.3090003@gibfest.dk> <20140111.143644.41639035.sthaug@nethelp.no> <52D15185.50802@gibfest.dk> X-Mailer: Mew version 3.3 on Emacs 21.3 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: lev@FreeBSD.org, net@freebsd.org X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.17 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 11 Jan 2014 15:24:45 -0000 > > I strongly disagree with the "almost always want a specific address > > family". I normally want to verify that the IP at the other end is > > alive, or get some idea of how to get there. If I want a specific > > address family I'm very happy to use -4 / -6 options. > > The IP at the other end will, by definition, always be either v4 or v6, > so yes, you do want a specific address family - namely the family your > IP belongs to. If I have an *IP address* (either IPv4 or IPv6), ping/traceroute can select the correct address family automatically, given the format of the address. If I have a *name*, to be used with a DNS lookup: - The name might have only an IPv4 address (A). ping/traceroute can select the correct adress family automatically. - The name might have only an IPv6 address (AAAA). ping/traceroute can select the correct adress family automatically. - The name might have both an IPv4 and an IPv6 address. Only in this case is it necessary to actually specify the address family *if it is important for you*. (There are cases where I don't care, and would be happy to let the system choose the address family. YMMV.) Thus in the three of these four cases ping/traceroute can determine the correct address family automatically. In only one of the cases is it (sometimes) necessary to specify the address family. I definitely want a unified IPv4/IPv6 ping/traceroute. Steinar Haug, Nethelp consulting, sthaug@nethelp.no