Date: Thu, 24 May 2012 22:24:15 +0400 From: Aleksandr A Babaylov <.@babolo.ru> To: Luigi Rizzo <rizzo@iet.unipi.it> Cc: "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net>, sthaug@nethelp.no, net@freebsd.org Subject: Re: use of non-contiguous masks in address lookups ? Message-ID: <20120524182415.GA7893@babolo.ru> In-Reply-To: <20120524120711.GB59250@onelab2.iet.unipi.it> References: <20120524071055.GA50710@onelab2.iet.unipi.it> <20120524.094321.74735847.sthaug@nethelp.no> <98091B3E-B728-483F-99FE-C65BD82CA089@lists.zabbadoz.net> <20120524120711.GB59250@onelab2.iet.unipi.it>
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On Thu, May 24, 2012 at 02:07:11PM +0200, Luigi Rizzo wrote: > On Thu, May 24, 2012 at 11:19:54AM +0000, Bjoern A. Zeeb wrote: > > > > On 24. May 2012, at 07:43 , sthaug@nethelp.no wrote: > > > > >> every now and then the issue comes up on whether we still need > > >> to support non-contiguous masks in address lookups. > > >> I seem to remember someone (perhaps on this list) making a > > >> case for their presence, but forgot the details. > > >> So, does anyone know of a practical use of non contiguous masks ? > > > > > > I vote for removing non-contiguous masks. They are incompatible with > > > CIDR, which was introduced in 1993 (!). > > > > > > Non-contiguous masks have been unsupported in many routers produced > > > the last 10 years or so. > > > > Contrary I still know people using them and relying on it. Not sure on > > which version they are. > > > > I am not quite sure what micro-optimizations on legacy IP will help > > us after a decade or longer. Let it rest and die gracefully the next > > years. Of course, fixing bugs still considered good:) > > the point of my question was to get [f]actual usage information on non > contiguous masks, because i don't know of any (at least on ipv4, > maybe in ipv6 there is one). The answer does not have to affect > FreeBSD, if that is what worries you. Load balansing: #netstat -rnfinet | sed -Ee 's|([ .])[1-9][0-9][.]|\1XX.|' -e 's|([ .])[1-9][0-9][0-9][.]|\1XXX.|' | head -8 Routing tables Internet: Destination Gateway Flags Refs Use Netif Expire 0.0.0.0&0x101 XX.XXX.222.58 UGS 0 1241 vlan9 0.0.0.1&0x101 XXX.XX.246.254 UGS 0 1387 vlan1 0.0.1.0&0x101 XXX.XX.246.254 UGS 0 1568 vlan1 0.0.1.1&0x101 XX.XXX.222.58 UGS 0 1491 vlan9
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