IP Addressing. (IPv4)

An IP address is a unique number / address used to identify a device on a network. An IP address is made up of 32 binary bits, which is divided into a Network portion and Host portion with the help of a Subnet Mask.

The 32 binary bits are broken into four octets (1 octet = 8 bits). Each octet is converted to decimal and separated by a period (dot). For this reason, an IP address is expressed in dotted decimal format (for example, 192.168.10.12). The value in each octet ranges from 0 to 255 decimal, or 00000000 - 11111111 binary.

Below is how binary octets convert to decimal: The right most bit, or least significant bit, of an octet holds a value of 2⁰. The bit just to the left of that holds a value of 2¹. This continues until the left-most bit, or most significant bit, which holds a value of 2⁷. So if all binary bits are a one, the decimal equivalent would be 255 as shown here:

    1     1    1    1   1 1 1 1

 128   64  32 16  8 4 2 1 = (128+64+32+16+8+4+2+1=255)

And this sample below shows an IP address represented in binary and decimal.

192. 168. 4. 10 (decimal)

11000000.10101000.00000100.00001010 (binary).

 

Recommended Cisco Networking Goods and Exam Resources

 

Click to play video

 

  

 

 

 

 

 

                  Type of  Addresses in IPv4    

 

                  Public and Private IP Addresses

 

                  Reserved IP Addesses

 

                  Variable Lenght Subnet Mask  (VLSM)      

 

                  CLassless InterDomain Routing  (CIDR)

 

                  Network Address Translation  (NAT)

 

                  Dynamic Host Configuration Protocol  (DHCP)