Re: inet hosts question

[Matthew Seaman]

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

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

according to modern criterea.




interface is given a /8 netmask -- 127.0.0.1 is a Class A address
by this scheme.

        Cheers,

        Matthew

--
Dr Matthew J Seaman MA, D.Phil.                   7 Priory Courtyard
                                                 Flat 3
PGP: http://www.infracaninophile.co.uk/pgpkey     Ramsgate
                                                 Kent, CT11 9PW

reserved for class B allocations (65534 hosts per net). Some large Universities probably could justify a Class B allocation, but I don't think any single institution or body has ever put enough machines onto the Internet to justify having a whole Class A network to themselves Needless to say, this was incredibly wasteful scheme in terms of address space coverage. As the whole 'network class' thing was an early attempt to just shave a few bytes of RAM in internet routers by not having to store explicit netmasks -- an economy that was rapidly made obsolete by the falling cost and increasing capacity of hardware -- class based allocation is now completely obsolete and we live in a fully CIDR world. Except that is, for the 'Class D' and 'Class E' (Multicast and Experimental) ranges which still exist. It's also why the loopback

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