by Administrator
29. June 2009 22:32
• Subnet masks are used to make classful networks more manageable and
efficient, by creating smaller subnets and reducing the number of host
addresses per subnet to what is actually required.
• Subnet masks were first used on class boundaries.
• Example
– Take class A network 10.0.0.0 with network mask 255.0.0.0.
– Add additional 8 subnet bits to network mask.
– New subnet mask is 255.255.0.0.
– New subnets are 10.0.0.0, 10.1.0.0, 10.2.0.0, and so on with 65534 host
addresses per subnet. Still too many hosts per subnet.
• Example
– Take class A network 10.0.0.0 with network mask 255.0.0.0.
– Add additional 16 subnet bits to network mask.
– New subnet mask is 255.255.255.0
– New subnets are 10.0.0.0, 10.0.1.0, 10.0.2.0, …, 10.1.0.0, 10.1.1.0, 10.1.2.0,
…, 10.2.0.0, 10.2.1.0, 10.2.2.0, and so on with 254 host addresses per
subnet.
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Tags: networking