Network Fundamentals

IPv4 Addressing

1. IPv4 address is 32bit (4byte) long
2. The IPv4 address are unique and universal
3. The address space of IPv4 is 232 or 4,294,967,296
4. There are two notations are:
5. Binary Notation
6. Dotted-Decimal Notation

1. In classful addressing the address space is divided into five classes: A,B,C,D and E
2. Binary notation(First Byte)
3. Class A          : 0
4. Class B          : 10
5. Class C          : 110
6. Class D          : 1110
7. Class E           : 1111
8. Doted Decimal notation(First Byte)
9. Class A          : 0-127
10. Class B          : 128-191
11. Class C          : 192-223
12. Class D          : 224-239
13. Class E           : 240-255
14. In classful addressing a large part of the available addresses were wasted
15. Default Masks for classful Addressing

1. In IPv4 addressing, a block of addresses can be defined as x.y.z.t/n in which x.y.z.t defines one of the addresses and the /n defines the mask.
2. Finding  First Address:

Rule1: The first address in the block can be found by setting the rightmost 32-n bits to 0s
                Let the address:               205.16.37.39/28
                                                11001101 00010000 00100101 00100111
Here 32-28=4; So have to change last 4 bit to 0
                                                11001101 00010000 00100101 00100000  OR  205.16.37.32
Rule2:   At first mask have to represent in 32 bit then ANDing the given address with mask
Now;
Given address   11001101 00010000 00100101 00100111
Mask                     11111111 11111111 11111111 11110000 (28 1’s 1nd 4 0’s)
First Address      11001101 00010000 00100101 00100000 OR  205.16.37.32

1. Finding Last address:

Rule1: The last address in the block can be found by setting the rightmost 32-n bits to 1s
                Let the address:               205.16.37.39/28
                                                11001101 00010000 00100101 00100111
Here 32-28=4; So have to change last 4 bit to 1
                                                11001101 00010000 00100101 00101111 OR  205.16.37.47
Rule2:   At first Mask have to represent in 32 bit then ORing the given address with the                 complement of the mask
Now;
Given address                                   11001101 00010000 00100101 00100111
Mask Complement                         00000000 00000000 00000000 00001111 (28 0’s 1nd 4 1’s)
Last Address                                      11001101 00010000 00100101 00101111

1. Finding Number of addresses:

Rule1: The number of addresses in the block can be found by using the formula 232-n
Let the address:               205.16.37.39/28
Here n=28, So 232-28=24=16
Rule2: The number  of address can be found by complementing the mask, interpreting it as a decimal number and adding 1 to it.
Now;
Mask Complement                         00000000 00000000 00000000 00001111 (28 0’s 1nd 4 1’s)
Number of address                         15+1=16

One major topic discussed here is the IP (Internet Protocol) addressing, an interesting topic under data communication technology. IP address is assigned to a specified client (device) in a network for its identity and is presented in 32-bit (IPv4) with 4 octets separated by a period, for example: 10111001.00010010.11110001.10100011 or represented as 185.18.241.163 in decimal.
So, when discussing about this certain topic, you will encounter the words Classful & Classless IP addressing. What then is the difference between the two?
Classful IP - also known as the conventional IP addressing, is basically IP addresses classified under a Class with a given range and a default mask.
For the range, we have the following table:

Commonly, we only use Class A, B & C since Class D & E are for multicasting and experimental purposes respectively. By the way, notice that 127 is not included in the range because it is assigned for loopback, usually assigned to your localhost or your PC.
For its subnet mask:

So, for example, if you check your IP address using ipconfig, and shows you with IP address 192.168.2.100 and subnet mask of 255.255.255.0 — that means you’re under a Class C network. Click here for online Classful IP Calculator tool if you need help.
Classless IP – as defined by its name, it does not follow any Class as above. When you encounter and IP address with a subnet mask which is not 255.0.0.0 or 255.255.0.0 nor 255.255.255.0 that means that it’s a classless IP.
I am not really an expert on this topic,  but if you need to understand more in details about this, you can check this site.