From owner-freebsd-net@freebsd.org Fri May 27 05:54:34 2016 Return-Path: Delivered-To: freebsd-net@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 7BB8CB4C2B9; Fri, 27 May 2016 05:54:34 +0000 (UTC) (envelope-from mark.tinka@seacom.mu) Received: from the-host.seacom.mu (ge-1.ln-01-jnb.za.seacomnet.com [105.28.96.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 1D61C10CE; Fri, 27 May 2016 05:54:33 +0000 (UTC) (envelope-from mark.tinka@seacom.mu) Received: from [127.0.0.1] (helo=Mark-Tinkas-MacBook.local) by the-host.seacom.mu with esmtp (Exim 4.82_1-5b7a7c0-XX) (envelope-from ) id O7TN2U-0003O8-D5; Fri, 27 May 2016 07:54:30 +0200 Subject: Re: IPv6, ULAs and FreeBSD To: Kevin Oberman , tinc@tinc-vpn.org, "freebsd-net@freebsd.org" , Mailinglists FreeBSD References: <20160519124446.GB2444@box-fra-01.niklaas.eu> <20160523034855.GA37797@box-fra-01.niklaas.eu> <20160524061707.GA77980@box-fra-01.niklaas.eu> <20160526193602.GF49239@box-fra-01.niklaas.eu> From: Mark Tinka Message-ID: Date: Fri, 27 May 2016 07:54:30 +0200 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:45.0) Gecko/20100101 Thunderbird/45.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.22 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, 27 May 2016 05:54:34 -0000 On 27/May/16 06:11, Kevin Oberman wrote: > There are a lot of excellent reasons to avoid ULAs. There are a very few > good, or even so-so reasons to use them. The most commonly cited reason is > security which is almost always wrong. In almost 20 years of working with > IPv6 I have yet to see any valid security reason for using ULAs. There are > any number of excellent papers on this. > > The most valid use is when you can only get a /64 from your provider. RFCs > recommend a minimum assignment to residential customers of a /56 but many > providers seem to have missed this, so there is no choice. prefixes longer > than /64 are effectively not possible. IPv6 does not care, but the > supporting protocols , make a /64 or shorter assumption. More intractable > is that hardware also often make similar assumptions. As you learned, you > really, really don't waste your time trying to make it work. > > I really guess all of this needs to be in the handbook so people don't > waste time trying to do things that are documented to either not work or > not work effectively. And, unless you are really, really sure you need > ULAs, They mostly just break things. Fully agree. Mark.