The big difference is that 192.168.0.0/24 is not subnetted (well, kinda)
192.168.0.0/16 is 256 networks of 254 users. at least by RFC just as
176.16.0.0/12 and 10.0.0.0/8 are 16 networks of 2**16-2 users and 1
network of 2**24-2 users.
Jason
PS, David, cram hard for that CCNA, only about 75% is networking
knowhow, the rest is the ability to use completely crammed cisco
knowledge.
On Thu, 2003-09-04 at 14:35, David Woyciesjes wrote:
> David Z Maze wrote:
> >
> > David Woyciesjes <dwoyciesjes@comcast.net> writes:
> >
> > > Praveen Kallakuri wrote:
> > >
> > >> secondly, how can i split 1.x into different subnets?
> > >
> > > I'll have to look it up, but it involves using a subnet mask like
> > > 255.255.224.0 instead of the usual 255.255.255.0. This way you can have
> > > a subnet with space for only a few machines, instead of the 254 spots
> > > you get with using 192.168.1.x with 255.255.255.0 as the subnet mask.
> >
> > If you wanted four identical networks -- say, 192.168.1.0/26,
> > 192.168.1.64/26, 192.168.1.128/26, and 192.168.1.192/26 -- you'd set
> > the netmask to 255.255.255.192.
>
> But, do you lose the first and last network ranges?
>
> And, the usual 192.168.1.x IP range (with 255.255.255.0 subnet mask)
> that most people use for home, can be written shorthand as
> 192.168.1.x/24.
>
> > Q: Is 192.168.1.60 on 192.168.1.0/26?
> >
> > A: See if a bitwise AND of the address in question and the netmask
> > equals the network address:
> >
> > 192.168. 1. 60
> > AND 255.255.255.192
> > ---------------
> > 192.168. 1. 0 <== YES!
> >
> > Q: What does 192.168.1.128/26 mean?
> >
> > A: It means that the network address is 192.168.1.128, and the netmask
> > is a 32-bit word with the high 26 bits set. These get broken up into
> > four groups of eight ("octets"); the three highest octets have all
> > eight bits set, for decimal 255, and the last is 11000000, for decimal
> > 128+64=192.
>
> But, for the 192.168.1.x/26 network subnet, 192.168.1.128 can't be used
> for a computer in that subnet, because it's the address for the subnet
> section.
> Rephrased...
> Each IP Address subnet range, (say, 192.168.1.x with a subnet mask of
> 255.255.255.0) has a network address, which is the first IP address of
> the subnet- 192.168.1.0 in this case. And the last IP address is the
> broadcast address for that subnet - 192.168.1.255. That leaves 254
> address for machines on that subnet.
>
> Since we're using a 192.168.1.x/26 subnet, it gets broken down into 4
> subnets:
> network address - broadcast address
> 192.168.1.0 - 192.168.1.63
> 192.168.1.64 - 192.168.1.127
> 192.168.1.128 - 192.168.1.191
> 192.168.1.192 - 192.168.1.255
> ...which leaves only 62 available IP addresses in each subnet.
>
> Here's how this applies to home use...
> Say your home network has 30 machines. Assign them address between
> 192.168.1.129 and 192.168.1.190, and use 192.168.1.192 for the subnet
> mask. Now you can safely assume that any traffic from a 192.168.1.x
> address, that is outside your subnet, is spoofed. Or something like
> that... :)
> Also, you can create even smaller subnets if you like, too. I think the
> smallest usable subnet only allows 6 IP addresses.
> Yep, I'll definitely bring my books with me tomorrow...
>
> --
> --- Dave Woyciesjes
> --- ICQ# 905818
--
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# Jason Straw -- jstraw@resample.com #
# Resampling Stats, Inc. -- Systems Administratior, Web Developer #
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