Look up rfc1918, it details the private networks. Three major classes of private ipv4 as Kevin listed. In large networks, you will tend to see all 3 uses, typically with physical or security differences in them. They usually only touch in internal network peering relationships with a routing protocol.

Don't mix and match lightly (or do, but look up gns3 first), and learn CIDR subnet/supernet masking. Don't go by class a/b/c/d anymore, it's all cidr now, and with ipv6 it only gets worse.

-mb


On 03/08/2012 10:46 AM, Kevin Fries wrote:
Mike,

Just for your information, there is also a third lesser known range
172.[16-31].x.y

Each of the three ranges are available for private use, and are illegal
on the Internet.  Which you use is completely up to you and is generally
based upon your own individual needs.

If you take the first part of any address, and represent it in binary,
it will tell you the address "class".

0.... ->  Class A address
10... ->  Class B address
110.. ->  Class C address
1110. ->  Class D address
11110 ->  Class E address

10  ->  0000 1010 ->  Class A - Default mask is 255.0.0.0 - CIDR /8
172 ->  1010 1100 ->  Class B - Default mask is 255.255.0.0 - CIDR /16
192 ->  1100 0000 ->  Class C - Default mask is 255.255.255.0 - CIDR /24

Class D was reserved for multi-cast addresses.  Most of these you will
see in the 224.x.y.z range

224 ->  1110 0000 ->  Class D - Default mask is 255.255.255.255 - CIDR /32

Class E was reserved, but never used, and never will be now that IPv6 is
here.

Using a class A address reserves 8 bits for the network address (i.e.
10) and 24 bits for the hosts, which leaves you with 2^24 or 16,777,216
hosts - 2 (network broadcast, and network addresses)

Using a class B address reserves 16 bits for the network (i.e. 172.16)
and 16 bits for the hosts, which leaves you with 2^16 or 8,65,536 hosts
- 2 (network broadcast, and network address)

Using a class C address reserves 24 bits for the network (i.e.
192.168.1) and 8 bits for the host, which leaves you with 2^8 or 256 -
the same 2 addresses.

Your broadcast address is where all bits in the host part are 1, and
your network address is where all host bits are 0.

I hope this helps you understand the difference between addresses, and
helps you pick the right one for your needs.

Kevin Fries



On Thu, 2012-03-08 at 10:18 -0700, Michael Havens wrote:
What is the difference between the 192.168.x.y and the 10.x.y.z range?
They are both the private network ranges but why would one decide to
use one but not the other?

--
:-)~MIKE~(-:
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