determining the netmask

[Aaron Howell]

Let me try to make it a bit clearer.
There are a total of 4 bytes (32 bits) in a dotted quad (an ip address).
In every netmask specification, there is a left and a right hand side.
the right hand side specifies how many machines are referenced by the netmask, while the left represents the remaining bits.
Netmasks, in cidr notation are represented as ip/mask
E.G, what used to be a class c address, that is, 192.168.1.xx/255.255.255.0
is now represented as 192.168.1.0/24 (there are 8 bits, or 255 possible hosts on the right hand side, leaving 24 bits of unused mask on the left).
If you wanted a total of 512 possible hosts, then it would be /23, for 1024 it'd be /22.
The original class b (255*255 hosts) is /16
While the original class a (255*255*255 hosts) is /8.
Traditionally, bite boundaries were used for allcation of addresses, meaning you could only have a /24, /16 or /8 allocation.
With the introduction of cidr, its now possible to bundle several /24s into a /22 or /21 for example and have them all  routed to the one place
(this concept is known as supernetting)
and similarly its possible to route smaller lots of addresses to (e.g clients),
such as a /28 or /29 (16 or 8 ips) this concept is subnetting.
This is explained in painfully complex detail in any good book on tcp/ip.
Regards
Aaron
On Sun, Aug 18, 2002 at 06:11:08AM +0300, Octavian Rasnita wrote:
> 255 is 2 raised at 8 power.
> There are 3 of 255. This means 24..
> 
> Oh, sorry, my english doesn't permit me to explain better.
> 
> Teddy's Center: http://teddy.fcc.ro/
> Mail: orasnita at home.ro
> 
> ----- Original Message -----
> From: "Gregory Nowak" <greg at romuald.net.eu.org>
> To: <speakup at braille.uwo.ca>
> Sent: Sunday, August 18, 2002 2:10 AM
> Subject: determining the netmask
> 
> 
> > Hi all.
> >
> > I know that a netmask of 255.255.255.0 is a 24-bit netmask. I also know
> that 8 bits is a byte. However, I don't understand how it is determined that
> 255.255.255.0 is a 24-bit netmask. Can someone please explain this? Thanks
> in advance.
> > Greg
> >
> >
> > _______________________________________________
> > Speakup mailing list
> > Speakup at braille.uwo.ca
> > http://speech.braille.uwo.ca/mailman/listinfo/speakup
> >
> 
> 
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