Cisco® CCENT Exam Cram Notes : Ipv4 Addressing

1. Networking Fundamentals

4. IPv4 Addressing

4.1 Subnetting :

Subnetting is nothing but creating networks within a network. Subnetting allows an organization with a single IP address (Class A /ClassB /ClassC) to have multiple subnetworks, thus allowing several physical networks with in the organization.

Addresses are written using decimal numbers separated by decimal points. This is called dotted decimal notation of expressing IP addresses.

The different classes of IP addresses is as below:

Class Format Leading Bit Pattern Network address Range Maximum networks Maximum host/nodes
A N.H.H.H 0 0 - 126 127 16,777,214
B N.N.H.H 10 128 - 191 16,384 65,534
C N.N.N.H 110 192 - 223 20,971,52 254
D Not defined 1110 224 -255 Not defined Not defined
E Not defined 1111 240-255 Not defined Not defined

Network address of all zeros means "This network or segment.

Network address of all 1s means "all networks", same as hexadecimal of all Fs.

Network number 127 is reserved for loopback tests.

Host (Node) address of all zeros mean "This Host (Node)".

Host (Node) address of all 1s mean "all Hosts (Nodes) " on the specified network.

1. The address range and the corresponding binary values for the first octet of IP classes are as given below:

Class A
0. 0. 0. 0 = 00000000.00000000.00000000.00000000
127.255.255.255 = 01111111.11111111.11111111.11111111
0nnnnnnn.HHHHHHHH.HHHHHHHH.HHHHHHHH

Class B
128. 0. 0. 0 = 10000000.00000000.00000000.00000000
191.255.255.255 = 10111111.11111111.11111111.11111111
10nnnnnn.nnnnnnnn.HHHHHHHH.HHHHHHHH

Class C
192. 0. 0. 0 = 11000000.00000000.00000000.00000000
223.255.255.255 = 11011111.11111111.11111111.11111111
110nnnnn.nnnnnnnn.nnnnnnnn.HHHHHHHH

Class D
224. 0. 0. 0 = 11100000.00000000.00000000.00000000
239.255.255.255 = 11101111.11111111.11111111.11111111
1110XXXX.XXXXXXXX.XXXXXXXX.XXXXXXXX

Class E
240. 0. 0. 0 = 11110000.00000000.00000000.00000000
255.255.255.255 = 11111111.11111111.11111111.11111111
1111XXXX.XXXXXXXX.XXXXXXXX.XXXXXXXX

2. The range of numbers from 224.0.0.0 to 239.255.255.255 are used for multicast packets. This is known as Class D address range.

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