Date: Tue, 15 Apr 1997 11:25:02 -0700 (PDT) From: Random Junk <jsd@gamespot.com> To: freebsd-questions@freebsd.org Subject: Re: Subnets of all 0's/all 1's Message-ID: <199704151825.LAA02841@hudsucker.gamespot.com> In-Reply-To: <199704151739.MAA25341@d2si.com> References: <Pine.HPP.3.96.970415104251.15425D-100000@sunfire.cs.iastate.edu> <199704151739.MAA25341@d2si.com>
next in thread | previous in thread | raw e-mail | index | archive | help
Alec Kloss writes: > I did not know that this isn't allowed. I checked things out and RFC > certainly does imply that this is a no-no. In RFC 950, RFC 943 this > referenced as justification for this. RFC does not seem to use > imperitive language (you shall or you must) but something much less > harsh, as in > "When called for, the address zero is to be interpreted as > meaning "this", as in this network." > This policy seems a bit strange to me. the only reason it might be problematic is when using old routers that couldn't handle it. any cisco router with a reasonable up to date operating system can do it if you type "ip subnet-zero" > For example, take a subnet > mask 255.255.255.128 on a class C network (ie two sub-networks). By > the above rule, addresses xxx.xxx.xxx.0-127 would all be illegal. > So, you've just cut you available hosts in half for no reason. yeah, it's stupid. CIDR and variable length subnet masks have really made all this stuff invalid or irrelevant anyway. just chop it up and you should be fine. we have carved our class C into 4 networks, of varying sizes. network 1 - addresses .1 through .30 - netmask 0xffffffe0 network 2 - addresses .33 through .63 - netmask 0xffffffe0 network 3 - addresses .65 through .126 - netmask 0xffffffc0 network 4 - addresses .129 through .254 - netmask 0xffffff80 just make sure you set the netmasks right or your machines will freak out when trying to contact stuff off their subnet! -- Jon Drukman jsd@gamespot.com SpotMedia Communications How the drunk and the maimed both are dragged forward out of the arena like a boneless Christ, one man under each arm, feet dragging, eyes on the aether. (David Foster Wallace/Infinite Jest)
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199704151825.LAA02841>