Subject: IP Address Distribution Among Classes
Author: AllAboutIP
In response to: Classification Based On ClassId
Posted on: 12/15/2005 02:47:29 AM
As shown above, Class A devotes 7 bits to network ID which counts for 2^7=128 networks and 24 bits to host ID which counts for 2^24=16,777,216 hosts within each network.
So, only handful of networks belong to Class A. Who are they? Here is a partial list of them with the gigantic Class A network:
----Class A IP Address ------ Organization
--------------------------+-------------------------
3.0.0.0 3.255.255.255 --- GE
4.0.0.0 4.255.255.255 --- Level 3
6.0.0.0 7.255.255.255 --- DOD
8.0.0.0 8.255.255.255 --- Level 3
9.0.0.0 9.255.255.255 --- IBM
11.0.0.0 11.255.255.255 --- DOD
12.0.0.0 12.255.255.255 --- AT&T
13.0.0.0 13.255.255.255 --- Xerox
15.0.0.0 15.255.255.255 --- HP
16.0.0.0 16.255.255.255 --- DEC
17.0.0.0 17.255.255.255 --- Apple
18.0.0.0 18.255.255.255 --- MIT
19.0.0.0 19.255.255.255 --- Ford
20.0.0.0 20.255.255.255 --- CS
21.0.0.0 22.255.255.255 --- DOD
24.0.0.0 24.255.255.255 --- Various U.S. Cable Networks
25.0.0.0 25.255.255.255 --- Royal Signals and Radar Establishment
26.0.0.0 26.255.255.255 --- DOD
28.0.0.0 30.255.255.255 --- DOD
32.0.0.0 32.255.255.255 --- AT&T
33.0.0.0 33.255.255.255 --- DOD
34.0.0.0 34.255.255.255 --- Halliburton
35.0.0.0 35.255.255.255 --- Merit Network
38.0.0.0 38.255.255.255 --- Performance Systems International
40.0.0.0 40.255.255.255 --- Eli Lilly and Company
41.0.0.0 41.255.255.255 --- AfriNIC
43.0.0.0 43.255.255.255 --- Japan Inet
44.0.0.0 44.255.255.255 --- Amateur Radio Digital Communications
45.0.0.0 45.255.255.255 --- Interop Show Network
47.0.0.0 47.255.255.255 --- Bell
48.0.0.0 48.255.255.255 --- Prudential
51.0.0.0 51.255.255.255 --- Department of Social Security of UK
52.0.0.0 52.255.255.255 --- DuPont
53.0.0.0 53.255.255.255 --- Mercedes-Benz
54.0.0.0 54.255.255.255 --- Merck
55.0.0.0 55.255.255.255 --- DOD
56.0.0.0 56.255.255.255 --- USPS
57.0.0.0 57.255.255.255 --- SITA
58.0.0.0 61.255.255.255 --- APNIC
62.0.0.0 62.255.255.255 --- RIPE
63.0.0.0 63.127.255.255 --- UUNet
73.0.0.0 73.191.255.255 --- Comcast
80.0.0.0 80.255.255.255 --- RIPE
address devotes 16 bits to host ID which accounts for 2^16=65,536 hosts within each network.
Class C address devotes 8 bits to host ID which means that a Class C network can have up to 2^8 = 256 hosts hooked to its network.
Spencer
>
> On 12/14/2005 03:35:26 AM
AllAboutIP wrote:
IP address can be classified among 5 classes, based on ClassId
...................0........8........16.......24.....31
..................+--------+--------+--------+--------+
..Class A.........|0.NetId.|...........HostId.........|
..................+--------+--------+--------+--------+
..Class B.........|10......NetId....|.....HostId......|
..................+--------+--------+--------+--------+
..Class C.........|110.........NetId.........|.HostId.|
..................+--------+--------+--------+--------+
..Class D.........|1110.......multicast address.......|
..................+--------+--------+--------+--------+
..Class E.........|11110....reserved for future use...|
..................+--------+--------+--------+--------+
In humans friendly format:
....................Lowest Address....Highest Address
------------------+-----------------+-----------------+
..Class A.........|.....0.1.0.0.....|.126.0.0.0.......|
..................+-----------------+-----------------+
..Class B.........|...128.1.0.0.....|.191.255.0.0.....|
..................+-----------------+-----------------+
..Class C.........|...192.0.1.0.....|.223.255.255.0...|
..................+-----------------+-----------------+
..Class D.........|...224.0.0.0.....|.239.255.255.255.|
..................+-----------------+-----------------+
..Class E.........|...240.0.0.0.....|.247.255.255.255.|
..................+-----------------+-----------------+
where, 127.0.0.0 is reserved for loopback and inter-process communication on the local machine; all 0s refers to network itself; and all 1s is reserved for broadcasting.
Spencer
References:
