From owner-freebsd-questions@FreeBSD.ORG Fri Nov 14 16:43:03 2008 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 641101065687 for ; Fri, 14 Nov 2008 16:43:03 +0000 (UTC) (envelope-from m.seaman@infracaninophile.co.uk) Received: from smtp.infracaninophile.co.uk (gate6.infracaninophile.co.uk [IPv6:2001:8b0:151:1::1]) by mx1.freebsd.org (Postfix) with ESMTP id D670B8FC08 for ; Fri, 14 Nov 2008 16:43:02 +0000 (UTC) (envelope-from m.seaman@infracaninophile.co.uk) Received: from happy-idiot-talk.infracaninophile.co.uk (localhost [IPv6:::1]) (authenticated bits=0) by smtp.infracaninophile.co.uk (8.14.3/8.14.3) with ESMTP id mAEGgtqu083749; Fri, 14 Nov 2008 16:42:57 GMT (envelope-from m.seaman@infracaninophile.co.uk) X-DKIM: Sendmail DKIM Filter v2.7.2 smtp.infracaninophile.co.uk mAEGgtqu083749 DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=infracaninophile.co.uk; s=200708; t=1226680977; bh=cnT2FwYGzyo8tV RbEKtkX7gshDfn7I1R30Ne4TZfMIc=; h=Message-ID:Date:From:MIME-Version: To:CC:Subject:References:In-Reply-To:Content-Type:Cc:Content-Type: Date:From:In-Reply-To:Message-ID:Mime-Version:References:To; z=Mes sage-ID:=20<491DAA89.80808@infracaninophile.co.uk>|Date:=20Fri,=201 4=20Nov=202008=2016:42:49=20+0000|From:=20Matthew=20Seaman=20|Organization:=20Infracaninophile|User-A gent:=20Thunderbird=202.0.0.17=20(X11/20080929)|MIME-Version:=201.0 |To:=20Vincent=20Hoffman=20|CC:=20Gary=20Hartl= 20,=20=0D=0A=20FreeBSD=20Questions=20|Subject:=20Re:=20inet=20hosts=20question|Refere nces:=20<000001c94666$5eb02360$1c106a20$@com>=20<491D9699.5000103@u nsane.co.uk>|In-Reply-To:=20<491D9699.5000103@unsane.co.uk>|X-Enigm ail-Version:=200.95.6|Content-Type:=20multipart/signed=3B=20micalg= 3Dpgp-sha256=3B=0D=0A=20protocol=3D"application/pgp-signature"=3B=0 D=0A=20boundary=3D"------------enigBAEC01202EA545843180F478"; b=G57 QRR7QUyTQU37+sV2R9SWi62lw6ytlWU7MeyAnSxIfrdu616YXI7CCQYMv/z7rMTiF7m Trqmas2YTxMEmwG3E3xq+vIll9OyetAvPjnq63WrMhBvaJrX1BECxlkqgBKhfSVBSav TzSsuVZFfk2rNLh4XR0E2W9Qob93+eKCNY= Message-ID: <491DAA89.80808@infracaninophile.co.uk> Date: Fri, 14 Nov 2008 16:42:49 +0000 From: Matthew Seaman Organization: Infracaninophile User-Agent: Thunderbird 2.0.0.17 (X11/20080929) MIME-Version: 1.0 To: Vincent Hoffman References: <000001c94666$5eb02360$1c106a20$@com> <491D9699.5000103@unsane.co.uk> In-Reply-To: <491D9699.5000103@unsane.co.uk> X-Enigmail-Version: 0.95.6 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="------------enigBAEC01202EA545843180F478" X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.0.1 (smtp.infracaninophile.co.uk [IPv6:::1]); Fri, 14 Nov 2008 16:42:57 +0000 (GMT) X-Virus-Scanned: ClamAV 0.94.1/8634/Fri Nov 14 15:56:33 2008 on happy-idiot-talk.infracaninophile.co.uk X-Virus-Status: Clean X-Spam-Status: No, score=-2.9 required=5.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VERIFIED,NO_RELAYS autolearn=ham version=3.2.5 X-Spam-Checker-Version: SpamAssassin 3.2.5 (2008-06-10) on happy-idiot-talk.infracaninophile.co.uk Cc: FreeBSD Questions , Gary Hartl Subject: Re: inet hosts question X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 14 Nov 2008 16:43:03 -0000 This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigBAEC01202EA545843180F478 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable Vincent Hoffman wrote: > Gary Hartl wrote: >> I thought I could do it by using the /class ie /32 for class c but i c= an't >> remember what the class delegation is for that size of pool, I think i= t is a >> class B. > 192.168.0.0/16 for your example. > and yes this is a class B (not all /16s are though.) >=20 > the /x notation is called CIDR (classless interdomain routing.) > http://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing Class C surely? 192.168.0.0/16 is the RFC1918 Class C reserved range of 256 /24 networks. Yes, Class B networks were /16s, but the A, B, C... classification is derived from the number of leading 1's in the binary representation of the first octet of the address, not the netmask. Thus Binary: Decimal: Class: Used for: ----------------------------------------------------------------- 0000 0000 -- 0111 1111 (0 - 127) Class A /8 Networks 1000 0000 -- 1011 1111 (128 - 191) Class B /16 Networks 1100 0000 -- 1101 1111 (192 - 223) Class C /24 Networks 1110 0000 -- 1110 1111 (224 - 239) Class D Multicast 1111 0111 -- 1111 1111 (240 - 255) Class E Reserved, experimental Hence the first /half/ of the address space was reserved for class A network allocations (16777214 hosts per net) and half of the rest was reserved for class B allocations (65534 hosts per net). Some large=20 Universities probably could justify a Class B allocation, but I don't=20 think any single institution or body has ever put enough machines onto=20 the Internet to justify having a whole Class A network to themselves according to modern criterea. Needless to say, this was incredibly wasteful scheme in terms of=20 address space coverage. As the whole 'network class' thing was an early=20 attempt to just shave a few bytes of RAM in internet routers by not=20 having to store explicit netmasks -- an economy that was rapidly made=20 obsolete by the falling cost and increasing capacity of hardware --=20 class based allocation is now completely obsolete and we live in a=20 fully CIDR world. Except that is, for the 'Class D' and 'Class E' (Multicast and=20 Experimental) ranges which still exist. It's also why the loopback interface is given a /8 netmask -- 127.0.0.1 is a Class A address by this scheme. Cheers, Matthew --=20 Dr Matthew J Seaman MA, D.Phil. 7 Priory Courtyard Flat 3 PGP: http://www.infracaninophile.co.uk/pgpkey Ramsgate Kent, CT11 9PW --------------enigBAEC01202EA545843180F478 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (FreeBSD) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iEYEAREIAAYFAkkdqo8ACgkQ8Mjk52CukIxtngCfVgMF1YBvKRAaeHaQrtiCkTWk rKIAn2DqHp3cjIdzwM9nC9bHjmiF5eW+ =YNOA -----END PGP SIGNATURE----- --------------enigBAEC01202EA545843180F478--