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Possible Duplicate:
What are the essentials of a Subnet mask?

hi,

In all the machines having internet connections , i can see a value called subnet mask associated with the TCP/IP properties of the ethernet interface.

what is the logic behind it? or how can i calculate from a particular IP address?

I just read it from some blogs but it was not clear

Community
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Renjith G
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2 Answers2

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This is best answered by Wikipedia, see CIDR notation to understand the importance of subnet masks.

MaQleod
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The subnet mask is what determines how many clients are assigned ip addresses within that domain and how many subnets can be created. That is determined by the subnet mask. A 255.255.255.0 can have 254 hosts (clients with IP addresses) on a single subnet. With two subnets there are 126 hosts. While a subnet address with 255.0.0.0 with a single subnet can yield over 16 million hosts.

There is a simple calculator here that is useful.

Since this is only a simplified answer this wiki goes into greater detail.

James Mertz
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