Date: Wed, 11 Feb 2015 09:40:39 -0500 From: Eric van Gyzen <eric@vangyzen.net> To: Julian Elischer <julian@freebsd.org>, Matt Churchyard <matt.churchyard@userve.net>, "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: Re: Invalid subnet masks Message-ID: <54DB69E7.60602@vangyzen.net> 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>
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On 02/11/2015 05:51, Julian Elischer wrote: > On 2/11/15 5:55 PM, Matt Churchyard wrote: > >> >> 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). > >> I'm learning towards the opinion that they should be rejected unless >> the user specifically overrides it (with something like an ifconfig >> flag or sysctl). These valid use cases are so rare, I would favor making this an error in ifconfig, but also providing a flag to silence the message and accept the mask. The error message could even mention the name of the flag, to be helpful. For example: # ifconfig igb0 netmask 250.250.250.0 ifconfig: netmask should be contiguous and left-justified; specify "incontiguous" to override # ifconfig igb0 incontiguous netmask 250.250.250.0 # If it's just a warning, that warning will get very annoying to people who are forced to use such a mask. (They're already forced to use such a network!) Eric
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