[ale] IP Calculations

[Mark E. Schill]

Now what happens when you introduce IPv6?? :)



-----Original Message-----
From: Matt Shade [mailto:mshade at threekay.com] 
To: ale at ale.org
Sent: Saturday, December 15, 2001 12:47 AM
To: ale at ale.org
Subject: Re: [ale] IP Calculations

I'm not exactly sure what's being meant as "classless" and "classful",
but
basically, you have "default" subnet masks for Class A, B, C networks.
Your
default subnet masks are:
255.0.0.0        Class A networks - 0-127.x.x.x
255.255.0.0     Class B networks - 128-191.x.x.x
255.255.255.0 Class C networks - 192-223.x.x.x

These give you your basic Class networks. You can SUBnet these networks
using non-default subnets.

Subnet 255.255.255.4 is an odd subnet, but not incorrect. You basically
need
all the binary digits to be zeros on the right side, for example:

11111111.11111111.11111111.11000000
subnet mask of 255.255.255.192

11111111.11111111.11111111.11111100
subnet mask of 255.255.255.4

11111111.11111111.11111111.11110010
incorrect, since all the numbers to the right of the last contiguous 1
is
not a zero

You figure out how many nodes are available on a subnet by adding up all
the
zeros.
On a Class C network subnetted with 255.255.255.240
(11111111.11111111.11111111.11110000) you would figure the 0000 part,
and
get 15 nodes.

That's the basics of subnetting. Next class, we'll learn super-netting!

matt shade
www.threekay.com


----- Original Message -----
From: "Joseph A Knapka" <jknapka at earthlink.net>
To: ale at ale.org
To: <kenn at refriedgeek.com>
Cc: <ale at ale.org>
Sent: Friday, December 14, 2001 14:19
Subject: Re: [ale] IP Calculations


> Ken Nagorski wrote:
> >
> > OK, there is something you need to know.
> >
> > Is it classless or classful? if it is classful then
> >
> > 0-127 is a class A ( first bit 0)
> > 128-191 is in the clash B (first bits 10 )
> > 192-223 class C ( fist bits 110 )
> >
> > However mostly the world uses VLSM or CIDR, (classless) In this case
you
> > need to know how many bits are on for subnetting,
> >
> > Lets say 24 (255.255.255.0) bits are on... Then you have 8 bits left
for
the
> > network
> >
> > You need to calculate 2^8 - 2 = 254 ( this is the amount of useable
hosts )
> >
> > The network will be the lowest IP ( before you minus 2 )
> > The broadcast is the last IP in the block
> >
> > Ken
>
> Is it not true that a classess network may have any netmask
> whatsoever? That is, you could have a netmask with lower-order
> bits == 1 and higher-order bits == 0, like 255.255.255.4, or
> something? I seem to remember encountering a network that
> had such a netmask, but the details are hazy.
>
> Cheers,
>
> -- Joe
>
> ---
> This message has been sent through the ALE general discussion list.
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>


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