IP Addresses and Subnet Masks

IP Addresses and Subnet Masks

IP address typically using dotted decimal notation, in which an address consists of four integers, often called quads, octets, or bytes- between 0 and 255, separated by periods. Like an IP address, a subnet mask consists of 32 bits.

In decimal form, the subnet mask appears much like an IP address.  In binary form, each of the 32 bits has a value of 0 or 1. When you compare a subnet mask with an IP address, the address bits that correspond to the 1 bits in the mask are the network  identifier bits. The address bits that correspond with the 0 bits in the mask are the host identifier bits.

FOR EXAMPLE- A typical IP address and subnet mask, expressed in the decimal notation used when configuring a TCP/IP computer, appears as follows

IP address :         192.168.32.114

Subnet Mask:    255.255.255.0

 

When you convert the address and mask into binary notation, they appear as follows

IP address:          11000000  10101000  00100000  01110010

Subnet Mask:      11111111 11111111 11111111  00000000

 

Because the first 24 bits in the subnet mask have the value 1, this indicates that the first 24 bits in the IP address make up the network identifier . The final eight bits in the mask have the value 0, which means that the final eight bits in the address are the host identifier. If the subnet mask value were 255.255.0.0 instead, this would indicate that the network identifier and host identifier each consists of 16 bits. The division between the 1 & 0 bits can occur almost anywhere in the subnet mask, as long as both the network and host identifier are each at least two bits long.

 

                                    MCSE, Exam:70-293 -Windows Server 2003 Network Infrastructure