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Sub Net Mask Address


As I mention in earlier article network address will give when we make all host side bits zero. The main difference between class full and class less IP addressing is there is no standard bit position to divide network and host side in class less IP. But we had to tell what is the point that network and host side divide in this case. That is why sub net mask address comes to seen. Subnet mask address is also 32 bit binary number. The sub net mask address will give when all network side bits makes 1(one ‘s) and all host side bits makes 0(zero). I think you can take better idea by looking  following e.g.
e.g. 1
IP Addr: 192.168.1.1                                        11000000.10101000.00000001.00000001
Sub net mask: 255.255.255.0                            11111111.11111111.11111111.00000000
We can write both IP and sub net mask or can write like this, 192.168.1.1/24. Number of network side bits are written as “/n “ after the IP.   
e.g.2
Let say 192.168.1.1/26 and ask to find the sub net mask address relevant to this IP.
  11000000.10101000.00000001.00000001  ( IP addr)
  11111111.11111111.11111111.11000000     (there are 26 network bits, so there should be 26 one’s)
  255          .    255     .  255     .      192              (sub net mask address)

This is the way that we find sub net mask.

You may have a question about the difference about these. 192.168.1.1/24 and 192.168.1.1/26. The number of host address that can use in particular network is difference. The first one has (2^8 -2) number of hosts and second one has (2^6-2) number of hosts.The reason for decrease two numbers are the network address and broadcast address can not assign to the computers. 

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