INTERNET ADDRESSING

 

ICANN International Corporation of Assigned Names and Numbers.  A private, nongovernment organization that ensures each user has a unique IP address.

 

Four Dotted Quad Fields

Binary:  32-bit (IPv4) 128-bit (Ipv6) addresses.  Each field = 1 byte.  8 bits = 1 byte

Decimal:  Each quad with a value between 0 (binary 0~field off) and 255 (binary 1~field on)

 

INTERNET ADDRESS CLASSES

Class

1st byte

1st bit(s)

Network/Host Portions

A

1-126

0

8 bits/1 byte

126 networks

24 bits/3 bytes

16,777,214 hosts

0.0.0.0 to 127.255.255.255

0.0.0.0

Used when computer initializes and requests an IP address.  Source address is initially 0.0.0.0 until it is assigned an IP address

10.0.0.0 to 10.255.255.255

Reserved IP addressing for private internets

127 loopback:  Cannot be used as internet address.  Allows client/server on same host to communicate.  Ideal for testing/troubleshooting (127.0.0.1 localhost)

B

128-191

10

16 bits/2 bytes

16,384 networks

16 bits/2 bytes

65,534 hosts

128.0.0.0 to 191.255.255.255

172.16.0.0 to 172.31.255.255

Reserved IP addressing for private internets

C

192-223

110

24 bits/3 bytes

2,097,152 networks

8 bits/1 byte

254 hosts

192.0.0.0 to 223.255.255.255

192.168.0.0 to 192.168.255.255

Reserved IP addressing for private internets

D

224-239

1110

MULTICASTING:  Not routable.  Datagram targeted to a group that is identified by network address only.  (no host portion)

224.0.0.0 to 239.255.255.255

E

240-247

11110

EXPERIMENTAL:  Reserved for future use.

240.0.0.0 to 247.255.255.255

BROADCAST ADDRESSES (255) (Network and host portions cannot be 255)

Send messages to all network hosts and are used only as destination addresses.

Limited Broadcast

255.255.255.255

Used for configuring hosts when they boot up.  (Not valid for sending and receiving)  Can broadcast to obtain an IP address from DHCP or BOOTP servers.

Net-directed Broadcast

 

Used to broadcast to all hosts in a network. Assigned network quad(s) host quad(s) is/are 255

Subnet-directed Broadcast

Broadcast can be sent to all hosts within a subnet.

All-subnets-directed Broadcast

Has become obsolete ~ multicasting is preferred.  Broadcast can be sent to all hosts within all network subnets.