Date: Wed, 11 Feb 2015 08:30:28 -0600 From: Jim Thompson <jim@netgate.com> To: Julian Elischer <julian@freebsd.org> Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>, Matt Churchyard <matt.churchyard@userve.net> Subject: Re: Invalid subnet masks Message-ID: <580B0DA4-05B3-45B8-ACB9-27B9174D76A8@netgate.com> In-Reply-To: <54DB343E.7090008@freebsd.org> References: <7e069c1946454793b1c7e0be988877c4@SERVER.ad.usd-group.com> <DE405399-70FE-48A3-B550-992EDEB5C468@netapp.com> <ecc9027578ce45d7a0436e345aadc249@SERVER.ad.usd-group.com> <54DB343E.7090008@freebsd.org>
index | next in thread | previous in thread | raw e-mail
> On Feb 11, 2015, at 4:51 AM, Julian Elischer <julian@freebsd.org> wrote: > >> On 2/11/15 5:55 PM, Matt Churchyard wrote: >> >> I appreciate that it might be 'valid' as a binary mask, but I'm struggling to find any documentation anywhere that actually suggests that it's valid as a network configuration. The entire modern CIDR notation, and all the routing system & hardware built around it (that shows networks in CIDR form and will collapse routes) has no way of dealing with these subnets. > most can deal with it, just not optimally >> >> Are there actually valid use cases for these types of network? > yes. > I've had networks that were the first and last quarter of a /24, and the middle two quarters were separate nets. > > Sure, it made my skin crawl, but I was in a pinch to get more machines onto that /26. > all four were served by the same router so only one router needed to know.. > > I have however at times though we could think about making ifconfig at give a warning. > (but not an error). https://lists.freebsd.org/pipermail/freebsd-hackers/2011-April/034997.html Subject came up on -hackers in 2011 Quoting RFC-1219: "While RFC-950 allows the "ones" in the subnet mask to be non-contiguous, RFC-950 recommends that 1) they be contiguous, and 2) that they occupy the most significant bits of the "host" part of the internet address." Jimhelp
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?580B0DA4-05B3-45B8-ACB9-27B9174D76A8>