Date: Fri, 14 Nov 2008 09:39:07 -0800 From: George Davidovich <freebsd@optimis.net> To: freebsd-questions@freebsd.org Subject: Re: inet hosts question Message-ID: <20081114173907.GA98636@marvin.optimis.net> In-Reply-To: <491DAA89.80808@infracaninophile.co.uk> References: <000001c94666$5eb02360$1c106a20$@com> <491D9699.5000103@unsane.co.uk> <491DAA89.80808@infracaninophile.co.uk>
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On Fri, Nov 14, 2008, Matthew Seaman wrote: > Vincent Hoffman wrote: > > Gary Hartl wrote: > > > > I thought I could do it by using the /class ie /32 for class c but > > > i can't remember what the class delegation is for that size of > > > pool, I think it is a class B. > > > 192.168.0.0/16 for your example. and yes this is a class B (not all > > /16s are though.) > > > > 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 As a suggestion to the OP, installing the ipcalc port might help make things more understandable, or otherwise facilitate learning[1] about networking generally. The output is optionally coloured, so the first three bits of the Network address, for example, would appear in red to serve as a reminder that an address beginning with 110 does indeed define it as a Class C address. % ipcalc 192.168.0.0 Address: 192.168.0.0 11000000.10101000.00000000. 00000000 Netmask: 255.255.255.0 = 24 11111111.11111111.11111111. 00000000 Wildcard: 0.0.0.255 00000000.00000000.00000000. 11111111 => Network: 192.168.0.0/24 11000000.10101000.00000000. 00000000 HostMin: 192.168.0.1 11000000.10101000.00000000. 00000001 HostMax: 192.168.0.254 11000000.10101000.00000000. 11111110 Broadcast: 192.168.0.255 11000000.10101000.00000000. 11111111 Hosts/Net: 254 Class C, Private Internet ----------- 1. Handy utilities in conjunction with a requisite amount of laziness may be considered an adequate substitute. -- George
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