page 1 - © richard l. goldman ip address ©richard l. goldman january 10, 2002

- © Richard L. Goldman

IP Address

©Richard L. Goldman

January 10, 2002


IP Address• An IP address is a 32-bit binary number.

00000000000000000000000000000000• It is made up of four 8-bit binary numbers

separated by periods (dotted decimal notation).00000000.00000000.00000000.00000000

• Each 8-bit binary number is called an octet.• The maximum decimal value for each octet is 255.

111111112 = 25510

• Each octet is represented with a decimal value from 0to 255 (256 different numbers per octet).

0 . 0. 0. 0 to 255.255.255.255


Network and Host Addresses• An IP address is divided in to two parts:• Network Address:

– The Network Address indicates which network the IP address belongs to.

– This address is used to route IP datagrams throughout a TCP/IP internetwork.

• Host Address:– The Host Address indicates which particular

device within a specific network the IP address belongs to.


Network/Host Portions

• The Network Address is always the first part of the IP address followed by the Host Address.

• The number of digits assigned to the Network and Host portions of the IP address varies depending on the numbers of computers in a network.

??? . ??? . ??? . ???

??? . ??? . ??? . ???

??? . ??? . ??? . ???

Host AddressNetwork Address


Large Networks (Class A Networks)

• Class A networks will have many digits assigned to the Host portion of the IP address. (Leaving only a few digits for the Network portion.)

??? . ??? . ??? . ???

Network Address Host Address


Medium Sized Networks (Class B Networks)

• Class B networks will have half of the digits assigned to the Host portion of the IP address. (Leaving half of digits for the Network portion.)

??? . ??? . ??? . ???



Small Networks (Class C Networks)• Class C networks will have only a few digits

assigned to the Host portion of the IP address. (Which leaves a lot of digits left for the Network portion.)

??? . ??? . ??? . ???



Classes• IP addresses are divided into classes. The first

three classes represent unicast (point-to-point) addresses:

• Class A

• Class B

• Class C

• The classes are based on the number of host addresses that can be assigned.


Class A Network Address• A Class A address uses only the first octet for

the network address.

• The network portion of a Class A address can range from 000 to 126.

• This gives a maximum of 126 different Class A network addresses. (All 0’s can not be used for a network address because it is a reserved number.)

0 . ??? . ??? . ???


Lowest Number

Highest Number 126 . ??? . ??? . ???


Class A Host Address• A Class A address uses the last three octets

for host addresses.

• The host portion of a Class A address can range from 000.000.001 to 255.255.254.

• This gives a maximum of 16,777,214 different host addresses within a single Class A network.

??? . 0 . 0 . 1


Lowest Number

Highest Number ??? . 255 . 255 . 254


Class B Network Address• A Class B address use the first two octets

for network addresses.

• The network portion of a Class B address can range from 128.000 to 191.255.

• This gives a maximum of 16,382 different Class B network addresses.

128 . 0 . ??? . ???


Lowest Number

Highest Number 191 . 255 . ??? . ???


Class B Host Address• A Class B address use the last two octets

for host addresses.

• The host portion of a Class B address can range from 000.001 to 255.254.

• This gives a maximum of 65,534 different host addresses within a single Class B network.

??? . ??? . 0 . 1


Lowest Number

Highest Number ??? . ??? . 255 . 254


Class C Network Address• A Class C address use the first three octets

for network addresses.

• The network portion of a Class C address can range from 192.000.000 to 223.255.255.

• This gives a maximum of 2,097,150 different Class C network addresses.

192 . 0 . 0 . ???


Lowest Number

Highest Number 223 . 255 . 255 . ???


Class C Host Address• A Class C address uses only the last octet

for host addresses.

• The host portion of a Class C address can range from 001 to 254.

• This gives a maximum of 254 different host addresses within a single Class C network.

??? . ??? . ??? . 1


Lowest Number

Highest Number ??? . ??? . ??? . 254


Other Network Classes

• Class D addresses designate host nodes that receive broadcast messages (Multicasting).– 224 through 239– Addresses that are in the range of 224.0.0.0 to

225.0.0.0 are experimental, or are reserved for future use and don't define any network.

• Class E & F addresses are reserved for experimental and future use.– 240 through 254


SummaryClass Range

(1st Octet)

Max Number of Networks

Max Number of Hosts

A 0-126 126 16,777,214

B 128-191 16,382 65,534

C 192-223 2,097,150 254

D 224-239 (Multicasting)

E 240-254 (Research)

The network class of an IP address can be determined by noting which range that the first octet falls within.


Special IP Addresses

• Broadcast (Local network segment only)

• Reserved

• Loopback Test127. 0. 0. 1

0. 0. 0. 0

255.255.255.255


Private Network IP Addresses• The IANA (Internet Assigned Numbers Authority) has

designated the following IP Addresses for use within a private network.

• Class A:

10. 0. 0. 0 through 10.255.255.255• Class B:

172. 16. 0. 0 through 172. 31.255.255• Class C:

192.168. 0. 0 through 192.168.255.255

• External routers should disregard these addresses and not publish their location


Leading Binary Bit(s) of IP Classes

Class Binary

A 0

B 10

C 110

D 1110

E 11110


IP Address QuizClass Range # Nets #Hosts

A Public 0. 0. 0. 0 – 126.255.255.255 126 17M

B Public 128. 0. 0. 0 – 191.255.255.255 16K 65K

C Public 192. 0. 0. 0 – 223.255.255.255 2M 254

D 224. 0. 0. 0 – 239.255.255.255

E 240. 0. 0. 0 – 254.255.255.255

A Private 10. 0. 0. 0 – 10.255.255.255 1 17M

B Private 172. 16. 0. 0 – 172. 31.255.255 16 65K

C Private 192.168. 0. 0 – 192.168.255.255 256 254

Loopback 127. 0. 0. 1 – 127.255.255.255

Broadcast 255.255.255.255

IP Address Review



A Public

B Public

C Public

D

E

A Private

B Private

C Private

Loopback

Broadcast

IP Address Quiz



A Public 0. 0. 0. 0 – 126.255.255.255 126 17M

B Public 128. 0. 0. 0 – 191.255.255.255 16K 65K

C Public 192. 0. 0. 0 – 223.255.255.255 2M 254

D 224. 0. 0. 0 – 239.255.255.255

E 240. 0. 0. 0 – 254.255.255.255

A Private 10. 0. 0. 0 – 10.255.255.255 1 17M

B Private 172. 16. 0. 0 – 172. 31.255.255 16 65K

C Private 192.168. 0. 0 – 192.168.255.255 256 254

Loopback 127. 0. 0. 1 – 127.255.255.255

Broadcast 255.255.255.255

IP Address Quiz Answers

page 1 - © richard l. goldman ip address ©richard l. goldman january 10, 2002

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